That is correct. And neither is a full page write logged if the page is initialized from scratch. And even without WAL compression, the "hole" in the middle of

That is correct. And neither is a full page write logged if the page is initialized from scratch. And even without WAL compression, the "hole" in the middle of the page if the page is not full, is "compressed" out. That's not to say that FPWs are not a problem. The increase in WAL volume they can cause can be seriously problematic. One interesting thing is that they actually can often very significantly increase streaming replication / crash recovery performance. When replaying the incremental records the page needs to be read from the os/disk if the page is not in the postgres' page cache. But with FPWs we can seed the page cache contents with the page image. For the pretty common case where the number of pages written between two checkpoints fits into the cache, that can be a very serious performance advantage.