We are all intentional about _over communicating_ what we are working on and where we will need support from from each other. Everything else pretty much just flows naturally from that. There are (rare) times were I cannot progress on something that day because I need feedback from someone who will not be online for 10 more hours, but it is just a built-in assumption that this will happen and I always have other work queued up that I can do if I get stuck....
>> you can simply work on something else while that particular task is blocked.
This attitude is a recipe for massive amounts of parallel WIP, not to mention knock-on effects and blocking dependent work. "Planning for blockers"? You're either being intentionally simplistic or not really concerned with anything beyond your own work. Enter "useless managers" like myself who need to "needlessly interrupt everybody" to try and get things coordinated...
The vast majority of time in my career, if you have a minimum amount of decent planning, you won't get blocked because you can't talk to another person immediately. And on healthy organizations, even if you do get blocked, you can simply work on something else while that particular task is blocked.
If you really scrutinize all these availability claims, they pretty much all come down to lack of planning.
Planning for blockers, planning for communication gaps, planning for maximizing asynchronous work, planning for decisions that require specific people, etc.
So many people are horrified by the word "blocked" when it's most times an artificial block created by their own systems. If I can't move forward on something, I'll start on something else and come back to the other one later.