I'd strongly argue that for most people "90-95% compatible" means "not compatible" if it doesn't run the one AAA game they care about, and "could get it to work by messing with versions of other software" is incompatible with the words "perfectly usable".

If it doesn't work out of the box and requires fiddling, then it's at most "barely usable", it doesn't even meet the standard for "decently usable" much less "perfectly usable".