You're right that ping times, being round-trip travel times for packets, are meaningless without the context of where the packets are traveling from and to.
For Starlink, it's safe to assume the "from" is "from the user's Starlink terminal at their home".
The "to" is probably somewhere on Starlink's terrestrial network. It could be the near edge, the middle, or the far edge. That is:
- It could be the nearby ground station where the packets enter the terrestrial network from the satellite network. That would help tech analysts compare how Starlink stacks up against competing customer-edge access network technologies like DSL, DOCSIS, and GPON (and of course old school crazy-high-latency geostationary satellite broadband like HughesNet).
- It could be a Starlink data center "in the middle" of Starlink's terrestrial network, where all the cloud providers and CDNs could co-locate edge nodes (including game servers). So in this way, it could in fact be directly representative of the ping time you'd see in-game, at least for game services that choose to colocate edge nodes at Starlink's data centers.
- It could be the far edge where Starlink's terrestrial network connects to Internet backbone providers and peer ISPs. In this case it tells you the minimum ping time you'll ever see when pinging any host on the Internet from your Starlink-connected home.
The way the Question was worded suggests a couple possible misconceptions that deserve to be cleared up:
First, please note that although Starlink has talked about future plans for satellite-to-satellite laser links to create a mesh network of satellites, that part isn't up and running yet, last time I checked. So your VoIP call to the other side of the globe isn't being routed satellite-to-satellite across the mesh of satellites to the other side of the globe. Instead, it's being bounced off a single satellite to a nearby ground station, where it connects to their terrestrial network just like any terrestrial ISP would have. Because of this, Starlink service is only being offered in places surrounding a location where Starlink has been able to build a ground station, because any given packet you transmit must be able to hit a single satellite "in view" in the sky over your house, and that satellite must also be "in view" of a Starlink ground station (a big Starlink-owned dish, not a customer terminal) at the same time. So for now, Starlink is much more like a series of regional broadband access networks, NOT a long-haul Internet backbone that just happens to be orbital.
In my experience with terrestrial ISPs "physical distance" is by far the biggest contributor to [RTT measurements].
As anyone who's used VoIP or online gaming with others from across the globe knows, 200ms ping times are not uncommon simply because of the distance involved.
You're right about "physical distance" and you're right to put it in quotes, because the distance itself isn't the issue, because the signals travel at the speed of light. The much bigger issue is that most long distance paths on terrestrial networks go through a lot of routers and switches and other networking equipment, and each of these "network middleboxes" adds processing delay. A single overloaded router in your path could easily add 20ms itself, which is as much delay as four thousand miles of signal travel at the speed of light.
Starlink is more of an outlier, because nothing is "close" by terrestrial standards (being 300-400 miles up).
Starlink's satellites are indeed 300 to maybe even 800 miles up, but it's just 1 hop. So it takes 2-4ms to get from your home Starlink terminal on the ground to the satellite, and other 2-4ms to get from the satellite to Starlink's ground station, and the rest of the quoted "20-40ms" figure must come from processing delay in the one satellite itself, and in Starlink's terrestrial network.
Mentioning this number helps analysts realize that a LEO constellation at 300-800 miles is WAY better than old geostationary satellite broadband like HughesNet, for which the satellites are 22 thousand miles away, and where, after processing delays and other sources of latency, minimum ping times are in the high hundreds of milliseconds, to even a full second(!).
I know it's idealistic, but a far more useful number would be something like "% latency added", where it measured latency differences between theoretical maximum speed (unimpeded light travel) and observed latency. This would inform the consumer how well/poorly their specific network/ISP is performing in a general sense
This is basically what they're doing, once you realize that the latency added is a constant, not a percentage. That is, Starlink always adds 20-40 ms, no matter whether the rest of your path latency is tiny or huge. This is at least true for now, since the satellite-to-satellite global mesh stuff isn't operational yet. Starlink's latency-add doesn't scale with the overall latency of whatever path across the Internet your packets need to take, so it wouldn't make sense to give as a percentage. In comparison, as a Comcast Xfinity customer, when I ping their nearest router (presumably their CMTS) from my cable modem, I get a 10ms RTT, so DOCSIS as a customer-edge broadband access network technology adds 10ms in my case. So I can take that 10ms latency of DOCSIS as a residential broadband access technology and compare it to the 20-40ms latency of Starlink as a residential broadband access technology, and come to an understanding that if I switched from Xfinity to Starlink, I would expect my Internet ping times in general to have a net increase of 10-30ms.