The fingerboard crack is clearly visible in their pictures and disclosed in the description. While I don't agree it's a purely cosmetic flaw, it's not like they didn't mention it.
Copy/Paste from the ad:
This bass shows moderate to light play wear. Finish checking is present. The bass of the headstock shows significant checking, this is purely cosmetic. There is a hairline crack in the end of the fingerboard near the neck pickup (see pictures). This is not affecting playability.