They fixed that in pgbackrest a while ago: https://pgbackrest.org/user-guide.html#backup/block

It was a major pain point for my backups for years.

That's a fair point, and it's a known challenge with file-based backups on systems like Postgres. That said, some backup systems implement chunk-level deduplication and content-addressable storage, which can significantly reduce the amount of data actually transferred, even when large files change slightly.

For example, tools like Plakar (contributor here) split data into smaller immutable chunks and only store the modified ones, avoiding full re-uploads of 1GB files when only a few bytes change.