Good point about the spot size.
Imagine a Belgian waffle…
Let’s say you wanted to measure how deep the holes are, what would you do? You’d probably get something small, maybe a toothpick, and put it down into one of the squares until it touched the bottom, then you’d pinch the toothpick with your fingers at the top of the hole.
When you pull the toothpick out you could then use a ruler to measure from the point of the toothpick to your fingers to find how deep the hole is.
That would only work because the toothpick is able to fit inside the squares of the waffle. Now imagine you don’t have a toothpick, all you have is a broomstick. If you were to try to put the broomstick into one of the squares it wouldn’t fit, it would stop on the top of the waffle because the broomstick is too big.
If the measurement laser spot is bigger than the feature you’re trying to measure, it probably won’t work.
The holes in this window screen might not be measurable if the laser spot is a couple millimeters in diameter.