It’s not that the triangle doesn’t exist, but that the brain has multiple options for forming said triangle, only one of which results in the real image. Threw the following together to illustrate:

I was looking at a grid lattice wall paneling just this week which had the same effect. If the pattern is perfectly uniform, the eyes can’t distinguish between different features in it. The whole situation is a bit comparable to a stereoscope. Shifting the eyes out of plane with the pattern causes the false images to split vertically while the one true image remains. This isn’t an issue most of the time, but it does demonstrate how some situations invalid for stareopsis can be tackled with a simple head tilt.

Rangefinders aren’t usually looking at patterns in walls for example. Aircraft or ships don’t create uniform enough patterns. Yes it’s still an edge case, but I just wanted to explain my point that tilting the head does offer the brain more to work with, which in some confusing situations can be critical to correctly perceiving the situation.