I think the gooseneck wall is perpendicular to the door even at the floor
The thing is, this wall doesn't appear anywhere near parallel to the line connecting the two transporter disks on the foreground, even though that line is rather neatly perpendicular to the door wall...
There'd have to be some really weird lens phenomena at play to twist the line between the disks one way in the foreground and the gooseneck wall the other way in the background to create this great a discrepancy.
I don't think if you get a plan view of the transporter that those two pads are parallel to the door. I think they actually are nearly perpendicular to the door.