I mentioned rsync in my summary, in part, because the linked article mentions rsync. But mostly because the readers here would be somewhat likely to know the rsync algorithm, so I explained how it was different. As you say here, it is a common trait for any algorithm that does block level updating. This technique is, generally, called the "rsync algorithm", because it's what Tridge used when he made rsync. Additionally, the title you chose "Delta Copying", begs the comparison to rsync, and is generic enough that it really needs a TL;DR. A much better title would have been something like "Replication without receive-side disk reads".
I think you are under the impression that I'm diminishing Bvckup2 by saying it is just rsync? I believe my summary was neutral, explaining how it was different from rsync.