How did you come to that determination?
That’s not how the matchmaker works.
Here’s the section most relevant to you:
"Now let’s talk about placements in the new Role Queue world. To help us seed your role’s SR after initially completing placements, we’ve been tracking your match results as you play the three different roles for several months. We want to help identify your skill at each role, so we can place you at the SR that reflects that skill. If we do a good job at that, you’ll immediately start playing in fair matches. The more inaccurate we are, the more games you’ll have to play on that role until your SR can adjust properly to reflect your skill. This also means that the more games you played on each role, the more accurate we could be with your new role SR.
What happens if you’re a returning player, but you never played one of the three roles? Since we don’t any have data to help us guide what your new role SR should be, we turned to some interesting data science. We looked at the population of players where we did have data for all three roles, and asked questions like “How well does a typical GM skilled player who primarily plays damage perform on the other two roles?” We then duplicated that question across all skill tiers, and the three different roles. This gave us some guidance on how to adjust players who hadn’t played a role yet. We also temporarily increase your variance level for SR gains and losses, so in cases we’re incorrect we can adjust you faster to the SR that matches your skill."
The matchmaking system says otherwise.