As far as I understand this is downloaded data and they may offer model selection later on? If so they have little choice and putting your data in the user `/Library/Application Support` (or maybe `/Library/Caches` but that's a mess in itself) is what you're supposed to do.
With the various security changes in "recent" macOS, you can't modify your bundle and download files inside it, as it would change its signature and break the notarisation system.
The latter. A model update would then just be an application update. To answer my own question - if they want to allow a choice of downloadable models, then Application Support is the perfect place.
With the various security changes in "recent" macOS, you can't modify your bundle and download files inside it, as it would change its signature and break the notarisation system.