There is always value in trying something new and if it works better stick with it.
If, for example, 5.2 makes a difference in a brewer’s beer, my advice would be to test the water and adjust the water chemistry. This should allow the brewer to brew beers w/o using 5.2 in the future.
Here is an example from my brewing experience: After reading abut German lager brewing and the fact that their primary fermentation is done after about 7-8 days at 46 F I grew very disappointed with my lager fermentation times of 2 weeks or more. And those were even at 50 F. I kept looking around trying to answer the question why are they getting so much better performance that I do. First I thought it was the tall fermenters and their stronger circulation. But then I saw that even at home brew scale experiments in Weihenstephan they were able to ferment lagers below 50 F in about a week. So it couldn’t be the tall conicals. When Geronimo then posted about air raised yeast on the NB forum and how much better they ferment I gave it a try and it worked. With the same pitching rate and fermenting at 48F they are able to primary ferment a 12 Plato lager in less than 10 days. Up to this point I thought it had excellent yeast health since I was raising my yeast on the stir plate and used it fresh. I didn’t know that yeast can be even healthier than that.
At this point I still have to verify if that actually improved the quality of the beer. But healthier yeast is able to get closer to the attenuation limit which I found to be important and oftentimes difficult for lagers.
Given that I’m biased towards not adding nutrients to the wort I’d see this as a sign that the yeast is in need of something. Oxygen tends to be one of the big unknowns but you said that you use the mix stir and my tests of that technique showed that you can get to 7-8 ppm within 2 min of stirring. But you also like to brew higher gravity beers which need more O2 and the mix stir’s limit is ~8 ppm. Borrowing a pure O2 system and trying it might be an option.
But it may also be the added zinc that helps like you said earlier. But if that is truly the case then the statement that brewer’s wort contains adequate amounts of zinc is to be questioned.
I think I’ll eventually give a yeast nutrition addition a try in a side-by-side experiment. Just to see what the difference would be.