There's a lot of voodoo in wheel building. More than most areas of bike service. A number of wheelbuilders (using the term only in the most literal sense here) have started using locktite on nipples apply the same theory as your guy. Problem is that if a wheel ever gets to the state where it'll make a difference the battle had already been lost long ago.

A spoke nipple is nothing more than a nut, and the basic rules of threaded fasteners apply. Tension provides the tension that keeps them from unscrewing, and I'd no more expect my spoke nipples to magically loosen (opinion for what it's worth) than I would the lug nuts on my car.

I now use an anti corrosive paste grease on my nipples because my bikes get lots of weather exposure, including road and sea salt. Before that I used light oil for for 30 years. Never had wheels loosen, nor had corrosion issues.

BTW- except for certain unique situations, and certain modern components that may specify it, I don't think there's need to use any threadlockers on bikes. They've become overused, but to me threadlocker to a bike mechanic is like wood putty to a cabinet maker. A short cut to correct for work that isn't done right.