Won placement match, got worse team in next match

Played first match with 3 dias and 2 plats, we won easily and I was on fire sometimes.

Since unranked matches can swing a lot, to find out your correct placement, for the next match, I expected mostly diamonds / dia+master.

But… system bugged out: What I got was GOLDS and some plats!

???

After that… “match”… I was fortunately back to diamond games, but what the hell was that? Why waste TWO MATCHES of my time for nothing? What is your excuse?