Isn't the fuel pressure regulator doing what you expect the fuel pump relief valve to do?  That
is, when the fuel pressure exceeds a specified level, the relief valve/regulator bleeds off fuel
from the pressurized system to reduce pressure.  Admittedly, the fuel pressure regulation serves
other purposes in addition to limiting fuel pressure to reduce damage to the fuel pump,
connections, lines, etc.

Rob, the oldkayaker