Have they really though? iOS has always shared the same underpinnings as OSX. Although much hyped with Big Sur, iOS features have dribbled into OSX since at least Lion (more than 10 years ago). They’re still distinct operating systems (thankfully IMO) and rather than unify, iPadOS is a distinct entity.

People have been calling this since they acquired PA Semi, 11 or 12 years.

Well, he also called TinderOS, another thing that didn't happen.