[coldtea]

>'rule of 3s' is way too simplistic. It is on the beginner level. 3 is an arbitrary number anyway.

That's precisely why it's useful.

"On your discretion" would just lead to endless bikeshedding - as having a useful discretion requires that you are already advanced enough to not need such advice.

It's not that new devs really understand three to be some special number either: just a useful heuristic, which can be 2 or 4 or 5 if needed.