It’s not unusual for a B-movie’s title to have nothing at all to do with the actual movie – so the facts that there actually is a “Secret of the White Lotus”, and that it gets revealed before the end, already make this one at least slightly better than the worst. =P
Of course only slightly, since I have to admit that neither Dr. Dutchman Fu, nor his vacation, nor the gouda cheese he stores in a custom-designed receptacle in his car, had a huge bearing on the plot. Or even any at all. Dr. Fu and Admiral Watanabe know each other, though. They met at an international exhibition for the villainy industry about 2 years ago, and had a nice little chat. Their respective styles of villainy were too different to allow for any sort of direct cooperation, though, so they’re only acquaintances, not allies.
The other thread connecting the Dr.’s white Lotus to the plot is the name of Admiral Watanabe’s organization, of course. Which is not “White Lotus”…but, well, it could easily have been. It would have fit the stereotype perfectly, so it’s basically just a coincidence that the name is different.