We're really all saying the same thing. I just guess I'm not seeing the harm in giving a stocking "range" along with several caveats. (Make sure the minimum tank size for the fish is maintained, don't stock the same species unless mated pairs or you understand the risks of trying to mate them, take into account how the fish feeds (messy?clean?), etc.)
When I look back on my original "plan" for my 46g, I laugh at how many fish I had planned for in there. They were all size-appropriate for a 46g, but there were just too many. Then I started researching and ran across the variations of the "rules". After popping my eyes back in my head, I whittled down my list to a more reasonable goal. And as continual education goes, it got whittled down yet again as I started to stock my tank. I now have 3 chromis, 1 clown, 1 bangaii cardinal, and 1 y.clown goby in my tank. (About 2.5"/gal
of full grown fish, if you're counting.
) Even with an oversized skimmer and plenty of live rock, I think my tank is probably one fish over its capacity but will deal with it. I can't fathom the problems I would've had if I'd of tried to carry out my original (or even #2) stocking plan.
You're right though - "rules" that really aren't rules pervade all hobbies, industry... you name it. I think of the "rules" I use to do my job, and realize that only after having maybe 10 years experience do you understand when it's OK to break those "rules" or where the rules don't apply. Back in our hobby, look at the tank turnover rule: 10-20x your tank size, in gallons per hour... right? Well... after having MaxiJets and then switching to Koralias, I can tell you that 200gph out of a MaxiJet is NOT the same as 200gph out of a Koralia. We're using FLOW as a "rule" where we really should be using the water VELOCITY because that's what's really important. But should we throw out that rule? Personally, I'll still use it because it gives someone a reference - a good starting point - to explore what will work in their tank.
OK... I feel like I'm beating a dead horse, so I'll just sit on my hands now!