> It writes out and syncs the accumulated WAL records at each transaction commit, unless the committed transaction touched only UNLOGGED or TEMP tables, or synchronous_commit is turned off.

So wal is synced before commit returns, and if you power cycle immediately after, the wal is played back and your transaction is not lost? So it's fine?

It does not need to sync all writes, only the records needed to play back the transaction after restart. This is what all real databases do.