Every time I’ve taken 202 to DXB this year, it’s boarded from the lounge. MXP has been boarding from the other regular gate downstairs. Maybe there were some other days this year where MXP got lounge boarding though, I’m not sure.
Last year was not so consistent.

Not sure how it’s decided. But I always thought that the DXB flight should get lounge boarding every time, since it is technically their “flagship” flight to their home hub vs MXP as a 5th freedom route.
Boarding from a regular gate downstairs is a completely different (and cluster of an) experience compared to the serenity of boarding from the lounge: