YES... I'm confused about something in one of your earlier videos.
I've installed the native HA integration in UCR, but did NOT install the UCR integration into HA. Your video implied we need both and kinda glossed over that saying something like "just install both" to make it work right, but I don't think that's the case.
Everything works just perfectly with my (deliberate) one-way setup... The UCR3 can control and request whatever it wants from HA.
AND, I can still keep my 1300 HA entities clean on the remote side... you can explicitly set which entities you want the remote to see and bring in to the remote for use, right in the UCR web configurator. If I remember right, you seemed to imply you need to do that on the other side (within HA), but I've not found that to be the case. My UCR software has just the 15 or 20 entities i want it to have, not all 1300.
My guess is that you ONLY need the UCR integration for HA if you want HA to actually control the remote (rather than vice-versa), which I don't need to do... i follow the same advice you gave... i don't make automations on the remote, I only make them in HA. Therefore there's no case I can yet think of where I need HA to do anything with the remote.
However, if someone does make automations on the remote and they want other events in the house to trigger those on the remote, then yes, I think THEN they'd need to install the UCR integration into HA.
Does this match your thinking on this? Or can you confirm with the developer?