Why are people climbing so fast?

Yes.

Tell me how what they have said changes what I said.

The estimate is you are plat. The big lump of probability is in GM. So, it gives GM games, to give you the highest amount of increase in certainty improvement for the matchmaker.

If you keep winning that, then… that becomes dominant, and you RAPIDLY increase to that rank.

What they wrote doesn’t go against that method of matchmaking what so ever.