IndexBuildInterceptor::_multikeyPaths is mutated unconditionally on sideWrite() in primary's process memory but has no RecoveryUnit::onRollback hook.

An aborted txn will cause the multikey change to make it into durable catalog at commit-build ts, while secondary's interceptor (oplog-driven) never sees the aborted writes.

The primary believes the index is multikey, while the secondary considers it not multikey.