Operating system: Linux Mint 19
Graphics card: GTX 1660
Short description of error
Projection of one vector onto another traditionally results in a scalar; but Blender's Attribute Vector Math Geometry Node, in its Project mode, returns another vector. Additionally, I have no idea where this vector is coming from, as it does not seem to relate to the projection at all.
An alternative possibility is that it represents the less commonly referred to vector projection; but in the attached file, which I have edited (check inside Geometry Nodes.001) to project position onto itself, the z-coordinate of the result is consistently zero. By vector projection, it should be parallel to position; which it clearly can't be if it isn't even on the same ray.
In the meanwhile, I'm going to try defining my own scalar projection; but this behavior is undocumented and likely a bug. (The documentation on Attribute Vector Math describes Project as "the projection of A onto B", which is not helpful at all.)
Exact steps for others to reproduce the error
In the event that this is a runtime bug, I'm also enclosing a screen shot.
My expected behavior is that Project returns (A • B / B • B), or the component of A in the direction of B. It's been a while since I worked with linear algebra directly, and there's a very mild chance I'm mangling it in my head; but I can't figure out how z could ever be zero.