...and the immigration officers aren't even enforcing it uniformly
The fact is, you can do all the research you like. It may be that, for your particular circumstances, you don't need a Visa - but if the guy who's working on immigration that day interprets the rules different to anyone you've spoken to before, or if he doesn't know the rules, or if he's having a bad day and doesn't like your haircut, you're going home.
Bearing this in mind, if at all possible, get a Visa. And if you don't have a Visa, regardless of whether you need one or not, don't volunteer any more information to immigration than you absolutely have to, without lying to them of course.
I suspect the laws aren't well known outside the aviation community, and they are subject to so much interpretation, that it's hardly surprising that you get different answers from different people. But, as I said, the only interpretation that counts is the guy who's working on immigration the day that you arrive, so do whatever you can to keep him happy.
FFF
---------------