productKind property
Apple's kind: software or mac-software, exactly as sent.
It names the record's product type, not a platform. A universal
purchase that runs on iOS and macOS answers software; a Mac-only
listing answers mac-software. Reading this as "the iOS release" is
wrong for precisely the case it looks right for, which is why this
document has no platform field for it to appear to qualify.
Raw, with no closed vocabulary of ours beside it, and that is the one deliberate exception in these classes to a store's vocabulary arrives twice. An enum of ours over this field would be an enum of platforms, and there is no platform here to name — so the honest shape is Apple's word and a doc comment, rather than a vocabulary that would be read as an answer to a question the storefront does not take.
Implementation
final String? productKind;