innodb_autoinc_lock_mode = 2, real danger if not using AUTO_INCREMENT columns
As far as my understanding goes, if you're truly not using any auto-increment identity fields, then that isn't a concern and you should be ok to switch to innodb_autoinc_lock_mode = 2.
The warning is purely about the fact that auto-increment fields can't have 100% guarantee of staying in sync across replicas when interleaved is set because it allows multiple INSERT statements to occur at the same time so the order of INSERTs (and auto-generation of the IDs) can occur in different orders between replicas and the source.
This article goes into pretty good derail about the different values for that setting and their recommendations on when to use interleaved mode for performance reasons.