Wow, you are absolutely right! File > Export lets you export either the original (i.e. sans edits) or the edited version. However, in the latter case, the date changes to current date! Thanks for pointing this out; have updated the article to reflect this.

Further update: SnipTag app for Mac lets you add and edit IPTC metadata (date, location, description, keywords and 20+ other tags) and also export photos with metadata embedded. Furthermore, it overlays dates, locations and a summary of descriptions as visible captions on photos. Photos can be exported with captions — a white border is added all round, with caption displayed below the photo. Useful.