Shit happens.
No need to search for how the "perspective" which is exactly called a "projection" works (just for me, I know it).
The problem I talked about was the following one if you'd draw it out with some construction lines)
look at the red and the blue line and at the red and purple area

If there would be a hard edge the Tibia anvil would be significantly off.
If there is a soft edge it might be alright - but it is really hard to say, fact is that the tibia peak of the anvil is placed to far at the left.
However:
If the edge is hard the plane is symmetrical
if the edge is soft the plane is asymmetrical
that was what I was talking about exactly.
Although it also always depends how you render it with limited pixel space.