You supposed right! You can think of the stock system as a return system, except it returns inches from the fuel pump with a ball and spring. The return never technically leaves the tank so it's always metered right at the pump.
Now for some math:
fluids are subject to p=r*g*h : r is rho (density), g is acceleration (usually gravity) and h is the difference in height. When we're talking about a return style system, there isn't a pressure difference between the regulated pressure in the tank and the fuel rail because there isn't a difference in height. This is looking at the car from top to bottom.
Now here's why it matters. When a car accelerates or brakes, it's producing positive and negative acceleration forces or (g's), usually in the magnitude of 0-1 for a normal car. Now the "h" in that equation starts to matter because the acceleration forces are lateral now. This means that if there is a length difference of 12 feet from the tank (the spot at which it's regulated) and the fuel rail (the point at which pressure matters) then we're looking at a pressure difference.
Gasoline @ 60* has a rho of 711kg/m^3
Assume .5G positive acceleration .5(9.81/2 m/s^2)
Assume a distance of 12 feet from the gas tank regulator to the fuel rail (3.6 meters)
deltaP=711kg/m^3 * 1/2(9.81 m/s^2) * 3.6 meters
deltaP=25.08408kPa or 3.63 psi.
This means that if the stock regulator is set for 410kPa (59.46 psi) then the front of the car will only see 55.83 psi when you're accelerating at 4.9m/s^2. The exact opposite would happen when you're braking (higher pressure in the rail than the regulator).
By moving the regulator to the same "h" as the fuel rail (or next to the fuel rails) then you can always have a consistent pressure. The fuel rails should have the same pressure just before the the fuel enters the fuel rails, and throughout the fuel rail itself (unless the fuel line or fuel rail is a restriction). 700+hp can be made on -6 hose so I don't think the typical LNF guys are anywhere near this restriction.
Correct me if I'm wrong LT1 (and I suppose I am) but I always thought the benefit of a return system was that all the injectors in the rail got the same fuel pressure because the fuel is allowed to travel through the whole rail before returning the excess pressure "Bleed off" to the tank?