Availability Group with log backups to NUL
No, you aren't missing anything except the opportunity to do a point in time recovery of the database.  AG's protect you from MOST hardware failures but they don't protect from user errors that drop a table or truncate data. Even if the business didn't have a SLA for RPO I would have log backups running as a DBA just to cover things, but you can backup to DISK='NUL' and the log will clear just like you backed up to a regular disk file.