I suspect what is happening here is that after you have deleted collections you do not want (and from what I can tell you appear to be doing that correctly) there is a delay while Roon and Tidal synchronise the deletion. Until Tidal removes albums in the deleted collection from your favourites list then reinstalling Roon and choosing a single collection may still result in Roon importing the albums in the deleted collection while they remain favourites in Tidal.
That seems a more likely explanation than some variation in the list of albums making up a collection.
Until Roon and Tidal synchronise deletions, you can hide the albums from view as set out above. It may be that clearing your Tidal cache will assist but it can still take some time for Roon and Tidal to synchronise.
I have left notifications for devs above and they may have more to add (or correct if I am mistaken !).
I have closed the thread as it was degenerating outside the forum guidelines.