I'm interested in where this nugget is too.
The maintenance free instructions for Wagobox clearly instruct you to reduce the maximum current for the terminals and also the maximum aggregate current which they state is the number of phase conductors * OCPD rating but they also say there are some situations where this may not be the case. I've taken that to suggest that as the maximum current in an RFC is limited to 32A it's within the 50A aggregate limit and therefore it's acceptable to put both joins in one box.