OED does indicate that “Good night” can be used as a greeting, but it’s unusual (and certainly in BrE, it would be unusual to the point of downright oddity):
- a. Expressing good wishes on parting (or occas. meeting) at night or before going to bed.
OED’s earliest citation for this meaning is from around 1496. It’s not obvious that any of its citations show usage on meeting, though.
- Chiefly Caribbean. Expressing good wishes on meeting during the evening. = Good evening int.
OED has citations from 1844 to 2009 for this usage as a greeting meaning “Good evening.” They have found evidence for it, as you have; but finding evidence is no indication of how general the usage is, in the Caribbean region or elsewhere.