Originally Posted by yamatadragon
The reason is simple: DO NOT USE TRIXIE'S RENDEZVOUS'S! If you stumble upon a Trixie's Rendezvous, ignore it. The "powers" she gives you (unlimited coins, unlimited super jars, unlimited Funk Vacs, never run out of air underwater, any presents you find have twice the stuff inside, any food you eat will heal you twice as much, instant height on bouncy fungus, unlimited funk) are considered "cheats" and disable the achievement from unlocking. I can't say for sure if the Permanent Super Jars bonus from the Hyper Funk Zones disables the Achievement as well.
I'll add this as a possible/likely reason in the guide, but I'd like some feedback from anyone going for the achievement or that has attempted it, as to whether or not this was a factor in them unlocking/not unlocking it (though it sounds about right).