Yeah, while the icon name used in mod wouldn't even have to be the same it is. Prototype is also matching at
data\core\prototypes\utility-sprites.lua lines
488 (starts the default category)
801 (fuel_icon)
In this mod prototype:
data.raw["utility-sprites"]["default"].fuel_icon = {
filename = "__SmoothWarnings__/graphics/fuel-icon-red.png",
priority = "extra-high",
width = 64,
height = 64,
flags = {"icon"},
scale = 1.4
}
All other warnings are done in same way, and if i made a single typo it would usually give a warning at start, but i don't see. May need to go ask devs support if they hardcoded the icon accidentally or something.
Edit: Started at https://forums.factorio.com/viewtopic.php?t=126391