It's not clear what kind of motherboards are in either of those systems, but given their price point, it's a safe bet that they are not the higher end motherboards that have the 'upgrader' in mind (i.e. they want you to buy more system instead of get 2 extra sticks of RAM). And just because a chipset/CPU can support X amount of RAM, doesn't mean that the motherboard physically has to (which is probably the case here).
It's possible the systems could have a hard limit in the BIOS that could be removed with a non-stock image (at the risk of voiding your warranty or system instability), and it's also possible the motherboard manufacture (most probably Dell and Lenovo's MB offshoot company) put a physical imitation on the memory lanes or something of the like, either to save money in production costs or as a specific design decision (thermal issues, etc.).
So to answer your actual question:
Should I try my luck and put 64GB RAM into them or wait?
If you already have the 64GB of RAM, you won't recognize more than 32 on one of those systems but you might have a chance if something like a BIOS update can fix that (though I doubt they'd double from 32-64 over a BIOS update), so chances are you'll be stuck at 32GB on one of those systems. And I'm not sure what you'd 'wait' for other than to build a different system with a different motherboard.
I hope that can add some clarity.