Matchmaking Bug - I queued as Jungle/Support & my friend as Fill, i got Support & my friend Jungle

We played a normal draft on euw as 3 premades. One queues Top/Jungle, one Fill and i queue as Jungle/Support. When we found a Match i got assigned Support and my premade that queued Fill got Jungle. So if both the Jungle and Support role is still available and you have one Player that queued Jungle/Support and one that queued Fill, then i expect the one with Jungle as their Primary role to be 100% assigned to Jungle while the Fill player takes what is left. Not really a big deal when you are premades but this could decrease your chances of winning in a SoloQ game.
I'm not sure what is factored in when the roles get assigned. Maybe they try to give "Fill" players as much diversity as possible and avoid giving them Support too much, considering there is already a ruling that protects you from being auto filled when you recently queued as Fill or Support. But i also played only support in my last games so this shouldn't really apply in this case. Here the last 5 Games we played: In my last 5 Games i queued Support/Mid and got Support all the time.
Not sure what exactly my friend queued, but in his most recent games he played: Support, Mid, Mid, Top, Mid (the Support game being the most recent). The 2 most recent Games were in a different queue though (Ranked Solo)