We have stated this numerous times.
Over the past year we have changed the rules for MM several times (see various patch notes).
Currently tier VI-X are capped at 2 and IV at 3 (assuming the queue times are not long enough to over-rule this)
There are so many people playing CVs at the lower tier that MM has to do what it has to do to make matches. This is why we have also changed the XP required to go from IV to VI.
People will progress to VI faster and there are more people playing VI-X battles so the number of multiple CV battles isn't as bad (unless you play in off hours).
But I digress.