When the explain_plan_cache.js test runs in jsCore_wildcard_indexes suite additional wildcard indexes are created. As a result the number of query plans reaches the threshold above which the automaticCE falls back to multiplanner subplanner. When the subplanner creates a composite plan from the $or branches, the whole query plan is not cached, e.g. the actual result is correct.

This change of behaviour was introduced in SERVER-118835.