I don't poo poo it as you write!
Its simply a rudimentary test .
Bosch doesn't present it as a rudimentary test, but a useful screening test (below from their brochure attached to an earlier post):
"To be able to repair a vehicle quickly
and cost effectively, the fault must first
be localized to a particular subsystem by
a process of elimination. Mechanical and
hydraulic faults are often analyzed first.
A variety of testers are deployed for the
purpose, including the back flow meter,
specially designed for testing of
Common-Rail injectors.
Back flow leak tester enables return flow
measurement on Common Rail injectors
(including Piezo injectors) on passenger
cars and commercial vehicle systems.
Adapters allow connection of many
injectors to the device."
Based on my limited experience and the above, it seems to me that if there are operability problems (i.e., smoke, miss, etc.) that can't be traced to another source, one of the first injector tests would be the leak-off test(s) to identify the problem injector and then the testing you propose to pinpoint the problem. Or, do you advocate a prophylactic regimen of pulling injectors (in the absence of apparent issues) and subsequent detailed testing?
PS - Seems there might be more than 1 leak-off test procedure - do you have procedures for leak-off tests at other than cranking rpms?