Sharding's writeConcern timeouts related to writes performed throughout the migration process should be bumped higher to prevent BFs. This write specifically caused the linked BF. Any other related writes that can be bumped without seriously affecting the rest of the system should be as well.
Proposing a bump to 30 second timeouts rather than the 15 second timeout that's the norm in sharding.
as we have 20 different kMajorityWriteConcern values defined in the anonymous namespaces but most still connected we can add the durations to write_concern_options.h
and use as instead of