Keeping an open mind and believing unsubstantiated claims are two different things. OK, I'm game. Let's break it down by the numbers. we'll assume 8ft of 1/2" line, running at 15psi, just for the sake of this illustration:
Fuel volume = what a pint? Probably less, but I'll give you the benefit of the doubt.
The fuel weighs somewhere around 1 lb.
15lbs /sq. in. pushing (or pulling) it, means it would take 16g's to overcome the force of the line pressure.
You still believe this is a major factor in fueling?