Scala only does single method tail recursion and rewrites it into a while loop. Cats and other libraries use a technique called trampolining which basically moves the frames to the heap (or a mixed technique where they do recurse a certain depth on the stack before switching to trampolining).

That sounds like it means that Scala doesn't support general tail-call elimination, so people don't write mutually tail-recursive code, instead transforming things that would naturally be expressed that way into a different structure that Scala does support.

Yes. It can be a major PITA, in certain problem spaces and I think most people don't pretend it's a great solution but ultimately accept it as a limitation of being hosted on the JVM.