After winning a match in fleet or Squad arena do you have a period where you are un challengable? I beat a squad in arena that took me below 10th but still only got 50gems it was 15mins to the prizes as when i checked my position i was over 20th again?
This is definitely true - but one has to be careful as the change effects a lot more than your fleet payout time.
I would suggest watching the payout times of people on your shard. If there is someone who is regularly over multiple payout times then there is probably a free spot around that time.
Reach out to that person, ask them their time and then plan accordingly.