They are indeed skewed to match the angle of the canal--I noticed it when I was photographing it but failed to mention it here...
I agree, the lift towers do appear to be on a skew in photo #5.
The Chandler Bridge here in Oregon is a vertical lift bridge similar to this one. It has a fairly large skew on the lift span in order to align with the shipping channel.
Is it just me, or is this bridge skewed to align with the canal?