@ClubSandwich - in my experience, they do.
On top of developing an insatiable thirst for aloe gloop, OH not only replaced everything in the house that could conceivably be substituted for an FLP product, she discovered a need for stuff she would never have considered before (handful of pills daily, shakes & other supplements, 20 different skincare routines...).
She also started forcing the gloop down our kids' necks, feeding them multivitamins and replacing their toothpaste with the vile fluoride-free FL stuff, despite our dentist friend being strongly against it.
I surreptitiously made sure the kids used my toothpaste at least once a day, and there doesn't seem to have been any permanent adverse effect.
As for the multivitamins, my OH had previously been rightly suspicious of the need for them, except in specific cases (our kids eat a well-balanced diet, and have always been in robust health). The issue came to a head when I pointed out to her that the FLP kiddy vitamins contained an artificial sweetener that she had previously treated as the work of the devil. She tied herself in knots trying to defend FLP aspartame as somehow 'more natural' than the common or garden stuff. I won that particular one, but she didn't talk to me for a few days (funnily enough, once it had been established that the kids were not having the FLP stuff, she no longer considered it so important for them to have supplement).
The boys had to wait for her to finally move out to be relieved of the daily dose of gloop, but their reaction to having fresh fruit with their breakfast said it all.
The depth of bottedness can completely defy any rational thought, whether financial, relational, medical etc...