Rockers flex.

I'll bet if you did the same check with light checking springs, solid lifters, and zero lash the numbers would be closer to spec.

These are the things you discover during the mock ups.

The only way you'd ever know if the higher lift actually made any more power is to test it.

I'll refer you to the rocker test Andy did on the TF heads........ And I have experienced similar results as that numerous times.