Where was this discussed? `=class` is still more numerous, and listed for OpenIndoor. https://wiki.openstreetmap.org/wiki/OpenIndoor#Rooms
There are other problems with `room=` eg `=toilet` vs `=toilets` https://wiki.openstreetmap.org/wiki/Talk:Key:room#Avoid_room=toilets (also how to distinguish open stalls with partitions vs actual room-like stalls with walls) 
The other major issue is `room=` `=shop` , `=restaurant` , `=reception` could be used to show the main `=room` . That's not covered by `amenity=` https://wiki.openstreetmap.org/wiki/Key:room#Avoid_these_values
Actually you have uniliaterally discouraged it? https://wiki.openstreetmap.org/w/index.php?title=Key:room&type=revision&diff=2711907&oldid=2621100