Not sure where th issue lies, but I cant get this to work just yet for objects behind other refractive objects. The refractive objects (even with affect all channels) come through as solid, hiding the stuff behind it)
A) Is it a general Cryptomatte limitation?
B) Is it a VRay implementation of Cryptomatte limitation?
C) Is it a limitation of the reader I’m using, namely EXR-IO 2.0 plugin for PS
It’s limitation. It’s also mentioned in Doc’s:
ah, ok thanks Svetlozar
Anybody know if that will be added some time down the line?
According to our Devs, it’s a limitation in the Cryptomatte itself, so we can’t tell what would or might happen.
Other render engines doesn’t support Refractive/Reflective Cryptomattes as well:
https://forum.isotropix.com/viewtopic.php?f=5&t=5019
Hello Morne
you have probably not read my answer in another thread after asking about it.
EXR-IO can read transparency behind objects. You can test it with the Arnold. Arnold has the Blend Function for this case.
Vray will have it probably so it is only the question of time till guys do it 
thanks
best regards