Reversal sending strategy is determined between you and the other endpoint. A reversal has enough information in it to not require it come on the same connection, but your mileage may vary.
Muxpool handles it well, you give it one of the strategies and it sends the reversal either on the next available channel or the channel it previously sent the request on (split by divisor). Split by divisor takes a field and divides "split-field say the stan , so if the stan is the same, the request and the reversal for it will be sent on the same channel.
-chhil