I realized after we approved and merged SERVER-73139 that one case which has caused bugs before is when the user has a non-simple default collation on the collection, but wants to override that with the simple collation. The "simple" collation is the default without any collation specified, so it just uses the default BSON/UTF-8 comparisons. This has caused bugs before because it is represented as a nullptr collation.

See for example SERVER-72224, SERVER-24433, and SERVER-71139.

Let's extend our testing to include this case. cc alyssa.wagenmaker@mongodb.com and fausto.leyva@mongodb.com who were involved in the review of SERVER-73139.