There is no such thing as a "macro" if its below 1:1 Shame on Zeiss.
1:1 ratio is a subjective value. You get more magnification with 1:1 macro on crop, than with 1:1 macro on FF.
Something like A7R (36mp sensor) allows you to crop a lot and get the same magnification of a 16mp crop sensor. So, technically, 1:2 macro on 20mp crop provides similar magnification to 1:1 macro on 12mp FF.
1:1 has nothing to do with megapixels; it is entirely governed by optics and means the physical size of the projected image equals that of the subject, ie a 1cm tall object results in a 1cm tall projected image.
Due to the cropping factor of an aps-c sensor though, you are effectively blowing up the projected image. So this means that for a crop factor of 1.5, a 50 mm lens will become 75 mm equivalent, and at 1:2 magnification becomes 3/4 magnification.
5D3, 5D2, Sony α6000, G16 | EF: SY14/2.8, V20/3.5, 28/2.8 IS, Ʃ35/1.4, 50/1.8, 50/1.8 STM, Ʃ50/1.4 EX, 100/2.8L IS Macro, 16-35/4L IS, 24-105/4L IS, 70-200/2.8L IS II, 1.4x II, 2.0x III, T28-300 VC PZD, 70-300L IS, Ʃ150-600 OS HSM S | E: SY12/2, 35/1.8 OSS, 16-70 ZA OSS, 55-210 OSS, SY300/6.3 ED UMC