In PrepareConflictTracker we assume TickSource is monotonically increasing and invariant when the clock goes back in time: https://github.com/mongodb/mongo/blob/c7bfbfeefcce9c73997e61d19c5efd7d57cf8971/src/mongo/db/prepare_conflict_tracker.cpp#L52-L62

In some platforms (MacOS) the clock is not monotonically increasing, we shouldn't rely on that.