I don’t think productivity comes from slacking, I think it comes from a communication tax. When you’re in the office you can just ask someone, at home you have to ask and wait and explain.
While working from home, those interruptions are dropped to 0. Any questions must come from some form of slack/email/etc that can all be ignored until I'm ready to look at them.
[0]https://heeris.id.au/2013/this-is-why-you-shouldnt-interrupt...
When I was in the office, most developers had headphones on when working and you wouldn't interrupt them at that time.
I definitely agree that if you're in the kind of role where you can turn off notifications and just put your head down and work, this has probably been a very productive year.