I have gone through some tests in my lab, by creating topology records that don't match my request and the responses were sent by round robin, each answer was coming from a pool. From what I understand, when a pool doesn't match with a topology record, the weight becomes 0, and that means all the pools will have equal weights ( all zeros) as no records matched, that's why the responses are coming back with round robin.
here is an example:
If there is no matching topology record that contains both the LDNS request source and a destination; therefore, the BIG-IP system assigns a score of zero to the pool.
you can check some other examples in this article: