That’s just a basic deduction from what we have been told about how SR works. SR is a user-friendly representation of MMR, which is constantly adjust towards your current actual MMR value.
If you don’t make any other change to the MMR, then by definition, your SR will catch up.
In the case of leaver penalties, which are divorced from any change to MMR, yes, that’s about the size of it.
In the case of an ordinary end-of-game scorecard, not really, because in that case MMR is changing, and then SR is changing to approximate the change in MMR.
Not really this, no. It’s more like you haven’t actually moved anywhere. The number that determines your matchmaking hasn’t changed, only the number that is displayed has changed.
But the display number is designed to reflect the underlying number, so inevitably the ‘punishment’ disappears.
Technically, if you’re right on the edge of a rank late in the season, it’s slightly more than cosmetic since SR is the value that counts for end of season rewards… but that’s a very marginal case.