My only gripe was the 90 minutes of server maintenance that occurred DURING the tail-end of the leveling event. Which, AFAIK, will NOT be added to or compensated for in any way.

This is not accurate, just as an FYI...
Xbox NA, Xbox EU, and PS4 NA were all given a bit of additional time to account for the second maintenance on 9/19.
PS4 EU finished their 24 hour window before that maintenance, so they were not affected.