The compression measurement was taken with a 80 Hz HPF. Depending on where the tuning sits, the SPL at the port tuning frequency might already be significantly reduced.
We'd also need to know the type of excitation signal. Was what was measured an RMS value (determined via sine sweep, stepped sine, or similar), or are the curves basically peak values created with stochastic noise or a multisine signal, which both have around 12 dB crest factor and would demand much less of the speaker.
That's good to hear, and I agree with the idea of checking the influence of slight vertical variations. I'd definitely also measure and compare different rotational axis - especially the very front of the speaker, also the center of the speaker.
To emphasize my previous point, I don't believe there's a fundamental reason why a turntable run should produce a completely different directivity chart than an NFS scan, especially if just in the high frequency region. But of course, both need to be set to measure the same thing. If the rotational axis and/or the measurement distance, or anything else of significance within the measurement setup or settings are different, there will be different results.
Because I don't think I've ever seen such an empirical comparison posted before, here's ours, with results, to provide something tangible, not just empty claims, to show both should generally yield close to the same result:
NFS:
Turntable:
