Yes, yes and yes. A DQA field labelled something like “Same species in each photo” or “Same species in all photos” limits the confusion over how “Same individual(s)” might be interpreted. (It’s a pity that “species” is ambiguous as to singular or plural, but I think other options such as “taxon” are more confusing.)
Totally agree that this DQA field should only be available for observations with multiple photos. And any edit that removes an image should reset this DQA field. As @jdmore says, the small proportion of observations that are still problematic can just be DQA’ed again.