In regard to the concept of drive degradation being "hidden" by controllers.
It seems to be a needful evil for the current applied art and science of rotating magnetic media at these price points. Yes, I suspect we "could" make media, heads, positioning methods et all that would be "true" non contact under most practical conditions.
The game is a paraphrasing of an older tech rubric- Cheap- Fast- Stable=pick any 2.
So the SMART ancestral concept was actually devised as an end run around those rules.
Setting a scoring metric for considering a "data element" as pass/fail is still a moving target.
Set your metrics too conservative and a drive becomes so apparently crappy that you would consider it as unsafe to trust. Set the metrics too optimistic and you replicate the ZIP drive impact- cheap- comparably fast for a floppy replacement- but dangerously unstable at times.
Some comments here invoked the Gibson drive tools. There is a Zip issue called Click of Death.
Mr Gibson did some excellent research into the cause, prevention, and recovery from the issue
That body of work gives some insight to how modern drives work and fail.
There's an element of Schrodinger's Cat indeterminate factors inherent in dimensions approaching or even exploiting quantum effects. Modern heads owe their ancestry of late more to a hall effect transistor than a magnetic coil. That allows flying head gaps to be larger for the same signal than older heads. Which paradoxically makes a head crash more devastating due to higher impact forces if from nothing else than SPEED! I could go on at length but It would be out of scope for the concept this thread is working out. Here's my topical constructive query .
In the form of a friendly challenge- Let's see who can share with our group the most useful Open Source usable from Linux tools to interrogate drive controllers as to true drive metrics.
Show us the code....
Oren