Not entirely true, my '11 CTS with direct injection monitors both low (from tank) and high (engine to rail) fuel pressure.
Agree, a good fuel pressure gauge (cheap ones may leak) is very handy for a "cranks but does not run". And spark plug lights and a set of noids (for injectors) are very handy.
Also helps that I have the best of both worlds, a Crossfire Coupe and a SLK320 retractable with the same drivetrain so can do comparison testing.
Happy, happy, joy, joy.