The matching algorithm may “see” everything, but the fact it is adding more weight to the top five may well skew the results. It is not inconceivable that a lower level player’s top 5 may well be comparable to a higher level player, but their next 25 are substantially less powerful. Depending on how the algorithm works it may effectively underestimate just how different these players actually are.
Personally, I’m not sure that this weighting of the top 5 heroes improves matchmaking.