It's easy to forget that our natural (non-enhanced) erections aren't ever as hard as an actual rock; if you consider the diversity of penis shape & size in conjunction with the variation men experience with
Erection quality, some "give" to the skin isn't remarkable.
I think we're our own worst critics, and I believe we notice even the slightest changes because we did, after all, get work done on our penis. I have heard many men describe their
HA,
PMMA, etc, as "rubbery" or "squishy", but seldom would these same men report that a partner complained of the same matter. Food for thought.
Also, there are ways to improve
Erection quality (assuming you aren't already at 100%), be it naturally or through ED medication.