For the current implementation, RelFieldCollation#Direction#reverse returns DESCENDING for STRICTLY_ASCENDING, and returns ASCENDING for STRICTLY_DESCENDING.
This is overly relaxed. In a strict manner, it should return STRICTLY_DESCENDING for STRICTLY_ASCENDING, and vice versa.
If the user needs to get the relaxed reverse direction, they may call collation.getDirection().reverse().lax();, as in many places of our code base.
Do you agree?