A reset would mean everyone starts at MMR 0, which is roughly equal to SR 2350. That definitely did not happen.
There are other valid non-reset reasons that could explain a 700 SR increase in role queue that Jeff describes. It is possible that you flex too much. Jeff said his support role SR was a full rating (~500 SR) lower than his tank SR.
I think it’s actually very very odd that you place 700 SR lower in previous seasons than you end, because placements start at the same MMR / SR as the end of the season. Maybe you do something odd during placements in normal seasons that didn’t happen in the beta season.
There is no reset at the end of normal seasons. Placements provide extremely typical SR gains and losses, for instance, a 9-1 record where things were not smurf like god tier, the SR gain is around 200, which is close to the average of 24 SR per net win (8 * 25 = 200)
In fact, I wouldn’t expect a 700 SR drop from a 0-10 placement. Are you actually saying you dropped 400 - 700 SR in placements every season, or did I misunderstand you?
Jeff Kaplan said no reset. Resets are bad. He also said they spent a great deal of effort to track good MMR per role leading up to the season.