The limit is per location, so if your two hubs are in the same location, then you are limited to 200 total.
When this limitation first arose about two years ago now, we were told at the time that it was to limit the number of device tiles in the app, because it took too long to load everything. Then we were told it had to do with the new edge platform. For quite a while it applied only to iOS, then it applied to both for a little while then it was removed from both for a little while and now apparently it’s back .
If you search the forum, you can find the old discussions. 
In the following discussion from August 2021, a staff member says they are looking at lifting the limit, but it came back again. 