If the WiredTiger eviction LRU algorithm chooses a page with no disk image, and only a very small count of items, it will end up as an on disk page with only a small number of records.

That isn't broken, but it's going to lead to poor fill factor and an excessively wide internal tree structure over time.

It makes sense to deprioritize those pages if eviction isn't having difficulty keeping up with a workload.