[Jeff Lee]

It's NHRA's testing procedure so they should have the tools necessary to do the job. If their lifter does not match your lifter's plunger height you "could" argue it is an invalid test if the test shows you are out of compliance. But if you want to avoid such issues (and I recommend you do), carry your own checking / solid lifter with the correct specs. And yes, the check is made at zero lash.
My opinion is finding every .001" of lift is not a real big deal. The rest of the cam specs is what really makes a big deal. I've been .015"-.020" under max lift and never felt it was a problem. Point is, like Ron Mattson stated below, give yourself a cushion.