Patrick,
Thanks for pointing this out. I almost added “at least on Windows” to my previous post but then thought “it can’t be that different on a MAC can it?”, and so didn’t 
I’m a Windows PhotoLab user and have never seen or used a MAC version of PhotoLab. Your post made me revisit the VP3 controls in Windows PhotoLab3 just now, in case I’d missed anything. What I found seems even stranger to me than what I thought was the case. I can draw lines for Horizon and Rectangle corrections but not for Force Parallel or 8 Points.
I can see that the ability to draw the lines would be (for me) / is (for you) a very quick way of deploying the corrections. The magnifiers would then just be the added extra that allowed accurate positioning of the endpoints to be done quickly without having to zoom in and move around the image. I also agree we would not want to lose the “draw the line(s)” ability in exchange for the introduction of magnifiers.