i use all my lenses on a crop sensor camera. Honestly is not big difference. I'm happy to have extra 1.6 reach.There are a lot of lenses for flower artworks or wildlife photography but a macro is a macro and that means, that it's (or above) 1:1. So a 20mm bug on a 22,55mm APC-C sensor at the close up limit is what I would define as a macro. Would mean (e.g. for my EOS 90D) that the bug would have 6186px in length with a total picture length of 6960px.
A 2:1 or 3:1 is also a macro but 1:1,5 would be a close-up photo.