I’ve been wondering about this for a while. Wouldn’t it make more sense to be a “solo focus” image if there’s a floating member/pair of hands? I would think when people search “solo” they are looking for a character completely by themselves.

disembodied penis: Disembodied parts count as characters, so in most cases this should not be combined with solo.

If you see any such posts being tagged with solo, it's likely a mistake.

Quoth the solo wiki:

What exactly counts as a character?

• Someone physically present within the scene, in whole or in part (including things like disembodied hands).

So yes, those posts shouldn't be tagged with solo and should be fixed.

Solo is frequently mistagged. Not infrequently I try to clean up posts tagged both solo and solo_focus.