this is a good question, and I try to reply somehow the same way I was when I had the same Q.
If you choose say a 90° on the shape snapping and then create a shape, what happens with the shape snapping is that if you rotate your shape very slowly, you will notice at a point while rotating that when you reach 90°, an orange outline and a "snap" appear for a blink of an eye. It means that your straight edge is at 90°
So try to use it again and never drop the view from your board while rotating the shape, it will make you see the snapping and hence explain for you if it is there for the use you need or if it is not your piece of cake
Hope this helps!
Hi, sorry for the very late reply.
So what you are trying to say is that the shape snap only applies to the shape, not to the grid.
I did see what you're talking about though. I'll continue to play around with it, and if I get any issue, I shall let you know.
I read it like that, yes