Yes, the fix only works for the simple case. Mutual (or deeper) recursion pattern could be detected, but it requires more work and the deinit would be more complicated as well. We have some ideas around optimizing deinit for tree like structures as well and I think the same approach could work for the mutual recursion case as well.
That said, as with any optimization, we have to consider how much work we put into it vs. how much we gain. I am working on some more widely applicable optimizations at the moment, but I would love to get back to this eventually.
If you have real world use cases that would benefit from this, I‘d love to hear about them. It would help us prioritize this work appropriately.