an error in geometry

[THHHomas]

In the file 02-single-view-metrology.pdf, page 8, 1st paragraph, "Finally, let’s suppose that we know that these planes are perpendicular in 3D. In this case, we know that from Equation 12, that
v1ωv2 = 0."
I guess it is an error. If two lines are in two perpendicular planes respectively, they are not definitely perpendicular to each other. therefore, the v1ωv2 = 0 is not definitely correct.