The aggregation_sharded_collections_pqs_fallback runs explains twice and verify the result is the same (after applying some query settings).

However, when the suite runs against 2 different mongos, the explain might end-up with 2 different results.
SERVER-118981 has moved the mongos dispatching logic from the runCommand to the _runCommandImpl for multiple routers.

The consequence of these changes are that the overridden runCommand  set by the implicit_query_settings_fallback.js and used by the suite will now have all the explain dispached against multiple mongos, while before the whole code would run against the same router.
The fix has uncovered the issue.

To workaround this issue, the aggregation_sharded_collections_pqs_fallback has currently enforced 1 mongos (see TODO associated to this ticket)

here an example of failing patch, where for router 1 it was suggested a COLLSCAN and for router 2 an IXSCAN