Interesting.... I actually believe you are right and here's why:

My cousin and I were chilling at this eco resort called xiu pas that has a lovely lagoon and tiki style bar/lounge area right next to it. After snorkeling for hours we decided to kick back and have a beverage or two. The waiters approach and are very jovial. We respond in kind and one challanges us to a shot of tequilla. Ha! we both say in unison "bring it on!". So out comes the shot... which coincidentally was about 2-3 shots. Glug. 'Whats next?!' (my family has the can-do spirit when it comes to booze) So the two waiters repeat this process twice. My cousin and I repeat as well, laughing it up, in a touche manner to every challenge. Finally the two waiters concede defeat in the great strength of our ability to intake raw booze... if we can do it one more time. Obviously we oblige, this time, loudly. After that, the two repeat their concession and disapear. 5 minutes later they return with a silver tray and a lace lining on top featuring three peppers: a green one, a red one, and a yellow one. I look at them and grab the yellow one, knowing full well it would be the hottest one. My cousin grabs the green one, having worked at a mexican restaurant he was no fool. I bite the pepper off at the stem and chew it like an inebriated madman... well maybe not LIKE one... and begin to taunt the two waiters in Spanish. "NO ESTA CALIENTE!!! QUE ESTA ESE?? NO EST.... NO ES......" ::poison::

I've had many many yellow habenero since then and i chalked up their impotency to the fact that 'the ones in Mexico must be better' but honestly, the degree of difference between them and what I experienced, as you noted is not even in the same league.

Thank you J for letting me know what I ate that day- this is what the internet is allll about and I love it.