First off, that whole 15 minutes thing is absolute bullshit. Maybe its a worst case if you were in truly deep thought over one of the hardest problems of the year. But most of the time you aren't, and it will be a few minutes Like around 1.
Obviously you don't think deeply about much of anything. It's often at least 15 minutes.
Secondly- your productivity doesn't matter. The team's does. Those interruptions- it means a team member needs help. They're blocked. Their productivity is at or near 0 until unblocked. If interrupting you costs 15 minutes from you but saves an hour for him, that interruption is worth it for the team. There are almost 0 of those interruptions that aren't a net gain. Now if you have a problem with particular people being too disruptive, that's a management/personnel issue you should bring up to your manager.
Guess again. Your review is based on YOUR productivity, not your team. Therefore it is what matters. I have been in jobs where I mentored juniors (answering questions takes waaaay more than 15 minutes), then got crucified on my review for spending too much time on "other stuff", and not doing my tasks. I got no "credit" for helping, "unblocking", mentoring or being an information source. None.
Also, your coworker who is so "blocked"? Has a question that they should either a) figure out for themselves without you holding their hand all damn day, b) do some searching on Google and or your internal wiki, or c) write on the group Slack so it is well formulated and able to be answered by anyone who is available.
Thirdly- not everyone works well in remote situations. Especially not long term (working remote for a day while you wait for a package/your maid/etc is a different matter). Very few people actually end up working as well as they do in an office- there are MORE distractions at home. And communications do not work as well- video conferences do not work as well as talking to someone in person. Even if you're one of those who do work well from home, you won't be as efficient as you would sitting near the rest of the team.
True. Some people can't manage themselves well at home. They have to have the conversations that make them feel important. They have to have their managers watch over them to keep them on task, and not bugging everyone else. They need to smell the farts of their coworkers, and get every illness so that they really feel like they are part of something. I for one find those people to be the biggest impediment to productivity.
Face to face conversations are waaay overrated, and for people who never learned to communicate via the written word. These are the same types of chumps who refuse to comment their code.
I am far, far more efficient working from home, or alone in an office after hours, than I am with everyone and their siblings, cousins and significant others interrupting me all goddamn day with stupid questions that can be answer by reading the goddamn wiki or doing a Google search and applying their fucking brain!