I think it's any locking knife regardless of size and/or a blade over 3", neither of which appear to apply to that one.
I'll repeat, it was a dumb thing to do but suggestions that he was threatening the guy or that he was the one who should be in jail just don't match up to the video.
Any locking knife above 2" (citation needed) carried in public needs a reason that a court will believe. You can't just say "in case".