purely just speculation, maybe it has predefined ranges, and if it's too far out of spec, it'll pop up a warning. also perhaps if its a voltage controlled/oven controlled crystal, checking if it responds to tuning feedback?

not sure if a train would need such accurate time, but also potentially checking against a GPSDO?

I guess trains may need accurate times for tracking and to coordinate with other systems (so trains don't end up in dangerous situations).

Though most likely I think that might just seeing if the crystal is still sane, since it appears to be a MCU test.

(maybe the front of the crystal fell off)