As soon as someone drops from matchmaking and it gives me my second role choice

Maybe this is not a bug and it's working as intended but I queue as support first priority and jungle second, 100% of the time. I NEVER get jungle in the first match set up. The ONLY time I get jungle is after someone has left and the games tries to restart matchmaking. Clearly whatever algo applies for the first setup, does not apply to the second. If it's working as intended, it's annoying. That is all.