Not sure if this works.

But Apple Maps exists as an OSX app so you could possibly use Apple Script to open the app, navigate to a point and take a photo.

Was wondering that myself. Presumably when you update your maps app or when the server updated, you have no more access to the old maps. Unless he took a whole lot of screenshots in preparation?

The URL to an Apple Maps tile includes a version number and numerous style options. It's possible the author knows about historical tile versions and updates the URL to fetch older versions, or has been archiving Apple's tiles periodically.

  https://cdn4.apple-mapkit.com/md/v1/vtile?x=1310&y=3166&z=13&scale=2&style=1&v=2002014&type=poi&lang=en&tint=light&emphasis=standard

Grabbed the tile from Apple's page here: https://developer.apple.com/maps/web/

The author also has their email address listed on their site if we'd like a definite answer.

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Edit: Looks like MapKit provides an easy way to take snapshots: https://developer.apple.com/documentation/snapshots

I completely forgot about Mapkit JS! I wonder how feature complete it is compared to Leaflet.

He could have done the whole “in preparation screenshot” thing using the js api. Or maybe there is a way to call and receive the old maps.