It took a while to find this interesting discussion about the ins and outs of "modern" hard disks (well, anything since IDE and SCSI took over): Are modern drives able to be low-level reformatted by an end user or is this strictly a factory OEM process?
Searching for "low-level format" does not yield much information online, because like you and @sawdust described, there is no possibility to do so anymore. The hard disk controller board abstracts all accesses to the disk and removes any direct access to the platters.
So, as to get in on why I'm searching for this discussion: I have an old 3.2GB Maxtor hard drive that I've kept nice and dry in the attic (no ESD wrapping though). It's been there since about 2006 when I used it last time and has not been physically moved or exposed to temperature cycles whatsoever. Turns out that the spindle starts rotating flawlessly still (no weird noises, just the regular silent whirr). What it does though, is a clicking noise from the head rocking back and forth a couple times, before the firmware gives up.
As there's no head crash or other mechanical failure (heads seem to work just fine), there's only one explanation I can see here: The sector track (hardware track #0) has demagnetized so far that the track is not recognized anymore and the firmware does not find sync/sector description/gap specs/etc and ultimately does not know anything about the platters at all.
Searching the net, I was trying to find some information about how semi-modern hard disks are initialized from the factory and if it would be possible to do such a re-initialization of the disk itself. I have access to modern oscilloscopes, wave gens and other lab equipment, so with the right info I may be able to find the original track, copy its waveform off the disk and amplify it enough to write it back to the platters in the right position.
Question is, has anybody done something like that or has any information about it at all? It seems like a project that would be rather fun to do for no other particular reason than "i can".
For reference: The disk is a Maxtor 90320E2, manufactured on 1998-08-08 in Singapore.