Moving "On Axis" when glued is confusing

I’m pretty sure this is wrong.

When moving a Group that’s glued to a face, Red (X) and Green (Y) axes highlight correctly when forced using arrow keys, but when the Up arrow key is pushed to force the alignment to the Blue axis (Z) the dashed line highlights blue - but that’s not correct since it’s not moving to a constrained Z vector.

It should be just a black dashed line because it’s stuck to the original plane (XY in this case, but could be anything).