IB is CBMM not SBMM. The only mode that has SBMM is survival & elimination. There is, according to many on this forum, SBMM in the shape of lobby balancing, but I have yet to experience any sign that either this is working to balance the teams or actually exists. What you also need to consider is that IB is probably poorly populated atm as there is no need to suffer to get 4 pinnacles if you have been playing since the start of the season so you are more likely to match either the sweaty tryhards or newbies that picked up the 30th anniversary pack but not much in between.