+Peter van der Walt you get it right. It does warn, thats right. But in many cases negative values just dont make sense.
It helps eliminating possible wrong user inputs when not allowing numerical inputs which never will lead to something useful.
Like negative laser power or negative laser diameter.
Warning if zero is great. I like that.
But on the same time letting the user do wrong inputs is the same as let him choose zero without a warning
User shouldn´t be able to go the wrong way.
Why not clamp/prevent? Makes user experience feel more trustful imho.
(btw: does that sound like a beginner mode with warnings / hints and an expert mode without?)