I see in the review in the Jan/Feb 2020 QEX that the minimum resolution is 1 kHz and scanning a crystal might give a close approximation of its resonant frequency but not much else.
I used nanoVNA Saver to scan a 4.915 MHz crystal with a resolution of about 4 Hz and it looks like I'd have the info necessary to calculate the motional parameters. I'm not sure if I'm trying to fool myself in going around an inherent limitation or not though. I measured a 3 dB BW of about 100 Hz but in another system I got 69 Hz. So that's a pretty big difference.
I'm still in the early stages of understanding the thing though.
73-
Nick, WA5BDU
Nick Kennedy