I have several that I have used on my PDP-8/a. AFAIK,
every controller
(including the RL8A) that talks to an RL02 will also talk to an RL01.
The 'Integrated Disk Controller' (or whatever they called it) on the
11/730 was claimed to support the R80 and the RL02. I've never heard of
one connected to an RL01.
I can't believe it's a hardware limitation (the interface is virtually
identical), but possibly the RL01 was not supported in software or
something. Or maybe it just works fine even though it was never supported.
-tony