Yeah, said that myself. A rowbike equivalent would make it obvious who’s on a rowing machine (it could be auto-selected when pairing a PM5 for example), and means we can just use the same roads as everyone else. Much less needed in terms of development support than any sort of dedicated rowing environment.
Also, an a Rowbike you go forwards. On a rowing machine you’d be rowing backwards, so it’d be a completely different (and a bit peculiar) experience I think. (Unless they implemented it as kayacking or canoeing, but those are very different arm-based motions so make less sense than the rowbike.)