Completely false. Win rates seems to play no role at all in the match making.

This is the result of how match making works. Lets have an example (i dont know the specific rule, but this is kind of how it works). I will only look at 1v1.

- All players starts with searching for other players in the queue with minimum elo difference. For example:

0-1 minute: max difference = 10

1-2 minutes max difference = 50

2-3 minutes max difference = 100

3-4 minutes max difference = 200

…
- A match is made if at least 1 player will match with another person.

For example: If someone of 1700 elo is waiting in the queue for 3,5 minute, then he can be matched against everyone between 1500-1900. This means you might be a valid target to play for him if your rating is above 1500. Thus you both get matched. You current searching range doesnt matter.

Since the number of players it less dense at the top, they have to wait longer before they found a match, thus their search range will increase. And thus they are matched against lower rated players.

This is just how the system currently works. You know that 100 elo difference means that your win chance on paper is still around 40%. It is not like you have no chance of winning those game. They might be a bit harder then usual. But you still have a decent chance of winning.