Update: Friend decided to go the safe route and did a DAP add. Thanks to everyone for the feedback.
What is your reluctance to adding nutrients?
He should be worried. I’m all about minimal intervention, but that means not doing less than the minimum necessary, such as depriving them of something they need to do their job.
The problem is that he probably isn’t going to see it as a problem until its too late. I would be worried about sluggish and stuck fermentations, especially with such low ammonia.
So here’s the thing - winemakers can either be dogmatic or pragmatic. In this case, dogma dictates your friend do nothing; pragmatism says to add nutrients to ensure you get from point A to point B with a bit more certainty.
It seems like a good lot to take a chance on. Lower brix, moderate acidity, and early in the season so it won’t get cold too fast. If your friend is against adding nutrients, why not go for it?