The test is not the placements, it's throwing a bunch of rounds into two account and then see where they end up over time. So throw 125+ rounds into each account in S4 and see where they end. It's too late to test accounts now being the season is over.
just placements at level 25 don't show much being QP is just so low effort now. It's easy to stat up and place higher, but most can't hold the newer rank if they play a bunch of rounds.
I have a guy on my friend list who landed with in 8sr of his main account on a new account even with going near 65% win rate in his 25 levels and playing with a bunch of us at 3.3k-4.1k.
then he rode the early SR boost to new comp players to finally break 3k, something he could not do all season. Then he slowly started to fall back down to 2.8k or so. Odds are due to lame game play late in the season.
but that's the test. You take two accounts going into a season. Throw bunch of rounds into each one and see if you win 54% on one but don't rank up and go 54% on the other can climb.
Odds are they will end up near each other in SR. Almost every player who admits to having a range of account and is willing to post them are always close to each other or at least with in striking distance. The whole silver on one and masters on another never seem to post their accounts.