I agree that there can be a skill involved in observation but isn’t there also a cost in attention and energy? In that case, it probably isn’t wise to try to observe anything and everything. Perhaps there are some principles for noticing when observation is likely to be worthwhile.
I also worry about generalizing too much from the example of fiction, which is often crafted to try to make nothing arbitrary. That property seems far less likely to apply to reality.
Quoting the article, you could probably find out it said, ‘observe everything and anything’, whilst excluding the definitive you pointed out, ‘all the time’. I of course excluded that point for a reason, though I did not point that out. I agree with you that it would be heavily exhausting, much like advising a singer to practice singing all the time. Observe everything and anything simply means a person doesn’t have to put a limit on what he/she should observe, not the length of time they should observe it. Your second argument was presented on my suggestion that a person should test out their observational skills on fictional work. It’s just my opinion, you might prove me wrong, someone else might prove me right, it’s all about opinions. But the book I recommended was beautiful, mysterious, and the clues while clear and logical, still proved largely unpredictable. It was one of those ‘we’re all thinking forward, because we believe it has to be forward, neglecting there’s really no law standing against it being backwards’ kind of logic.