I get lots of Pearl, Haven and Icebox. There aren't any weights for maps its all equal chance, it's just you get unlucky. The server has an ordered list of the maps like:

Split - Pearl - Fracture - Ascent - Haven - Icebox - Lotus

If the server finds 3 matches in the same millisecond: The 1st match found (that was 0.1ms earlier than the other 2) will get the 1st map of the list; the 2nd will get the 2nd; and the 3rd will get the 3rd. Once the list is exhausted, it just returns to the beginning and repeats it. While theoretically this isn't true Randomness, in practice for players it is functionally no different from randomness.

There is absolutely no logical, monetary, design or coding reason to have it work any other way. True randomness would require more ressources than the method explained above and creating weights by making one map appear more often than the others would also be unnecessary fluff that can only create more opportunities for bugs and inconsistent/unbalanced matchmaking.

I don't think there's anyway you could convince me that they increase the rate of certain maps without doing a census of over 10 000 players that all played during the same 8 hours on the same servers and found that statistically some maps appeared more. And even then I would question whether those 10 000 players are a large enough percentage of the population at that time.