I don’t think the perspective matters that much because that black rim at the back is at roughly the same depth as the picture so you only have to compare it to that. Only your red lines matter and they prove, that there’s a bit of space to the right while there isn’t to the left.
I love this in principle but I can’t use it myself. I‘m a very fast reader by default, basically already doing what the highlighting tries to make you do, without it needing to be there. The highlighting disrupts that for me. I end up stopping at every word and partially jumping back and forth. I do show this to people on occasion that aren’t as lucky as me with their reading speed and most said it helped them. Not all though.