Using the vanishing point assitant tool, placing two points gives you a horizon line and two rulers to draw along, but no vertical alignment to draw with.

To give proper perspective there should be a third axis generated that matches up perpendicular to the horizontal alignment of the two points.

I tried following the youtube video by Wolthera van Hövell tot Westerflier to set up a possible horizontal alignement, but it doesn't seem like a proper vanishing point set up.

This can be worked around by adding a parallel ruller assistant, matching the a right angle of the two points in the vanishing point assistant.

I like commenting on my own posts, however I don't want to accept this as the answer.
You can't easily make a right angled perpendicular ruler from any two points, it could rather should be done by the vanishing point assistant by default.