Well, yes and no.  While it's true that the test procedure in the service
manual for the lift pump is all about measuring fuel flow, and not pressure,
pressure is still a valid way to verify the health of the lift pump.  The
CP3 injection pump isn't nearly as sensitive to fuel pressure as the VP44
was, and will still operate safely at near-zero fuel pressure (so long as
there's fuel flow).  But, barring any kind of abnormal (and unlikely)
restriction, you can safely assume that the CP3 is being fed a constant
supply of fuel so long as your FP gauge registers some amount of pressure.

So, to me, an FP gauge is still plenty valid, and much cheaper than a flow
gauge.