I'm not seeing anything anachronistic about either term. "Seasons" is absolutely aligned to the way television series are still produced and distributed. "Box Set" implies physical media. Using the latter term to refer to something else sounds like a case of false advertising.
Apple offers refunds for unwanted digital purchases, and this description in Apple TV app:
When you purchase access to this item, you can permanently download it to your iPhone, iPad, Mac, or PC. Once downloaded, you can access this without an internet connection, and Apple can't remove it from your device.
Wait, so it's actually a standalone, DRM-free download? If that's the case, then while the term is still somewhat misleading, it's considerably less so than I assumed.
Not DRM free, but unlike most streaming services Apple TV will download purchased media via different countries or VPNs and has no time limit to watch the download. In practice, it "just works". Buying all 4 seasons individually would be 4x$13=$52.
