I mean, I've never come across Synology branded HDDs. I would have assumed they're just re-branded WD or Seagate. Doesn't make sense to me. They would have had

I mean, I've never come across Synology branded HDDs. I would have assumed they're just re-branded WD or Seagate. Doesn't make sense to me. They would have had to introduce additional identification checks just for "re-branded as ours". Nope. And part of the magic of a NAS is not necessarily having to have matching hardware. In addition to other design basics like using drives from different batches to minimise the likelihood of multiple failures within data-fatally small time frames. Monoculture is inherently more fragile; it's antithetical to good storage design.