I extracted this issue from an 2016 post, as the "recent" update to the SUMMARIZE behavior did not fix the issue described there ( https://community.powerbi.com/t5/DAX-Commands-and-Tips/Is-there-sth...
LaurentCouartou,
I have reported this issue internally: CRI 101349806, will post back once I get any updates.
Regards,
Lydia