Why does a Diamond 4 get to play against silvers and golds......... Esp in ranked.

I know that flex and solo q are separate mmrs. I also know that a Diamond 4 should never be able to Queue against silvers.

(BTW the team that lost was in promos to silver 5 flex when they got placed against a diamond)

I deleted all the stats because it has no bearing on the discussion as it is only about a diamond being matched with silver.