Confused Flex Rank 3v3

So, The new rank system for flex is nice, however.. Riot still believes that a powerful ranked 5's (Plat) can queue for Flex Rank 3's.. and play bronzes..... Not sure how Riot has the idea of matchmaking lowbies like that vs Plat or greater players... I have played many years with LoL and riot and has been a great experience with its ups and downs.. But to make a new flex rank system and not make it work properly, IF they were diamond/plat/gold.... in 5's, wouldn't you believe there rank queues would find higher rank teams then bronze to give them a battle? Please if riot can come up with a great reason why higher tiers should play low tiers in Placement, by all means explain.. I just got done with a flex 3's. (not placement) and had to fight against 2 Gold 1's and 1 Plat 3.. and my entire team was bronze 1.. Silver 5/ Bronze 3 and gold 5 on 5's and silver 5 on Flex 3's.