That latch lock is the long-eject-hook variant, which helps lever the connector off the header when you need to break the harness for service — a half-turn loose is a dropout, but a properly seated latch is solid.
Bulk packaging as listed.
Comparing against a sibling — 1-1871673-2
That part is a right-angle mount, while the 5499923-8 is vertical through-hole. The 34-position count here is a different density tier — you'd pick the 5499923-8 when you need the full 34 I/O lines and the vertical board orientation.