Is Time Blocking All or Nothing?

There's assumption here in this discussion that time blocking is either all or nothing. But I don't know that we have to go to the extreme of time blocking multiple hours every day and thus tie up our entire calendar. We actually all do some form of time blocking because we have a then for things to go to when we block up time. And what it does, that tells other people within my organization who have access to my calendar that I'm unavailable during the time because of focus.