If Apple will willy-nilly reject app store (both Mac and iOS) apps, retroactively change rules to kill competition (look up what they did with steam) and randomly start banning popular frameworks (electron apps are the latest victim), and still insist on being W3C non-compliant, in a blatant effort to force users and developers to their walled garden, developers need to grow a backbone and take Apple on where they can. If Mac users really want your webapp, Firefox/Opera.... are just an install away
In general, I could appreciate the decision to make a stance in this way on a personal level, but when evaluating a real landing page for a paid product from business perspective—which would be an inseparable aspect—I would not be able to recommend preferring “technically correct” over “actually working”.
This does not only hurt sales/business, but also causes stress to non-technical end users. All they experience is their browser exiting when they visit the page (thankfully, tabs are preserved on next launch); they are not concerned with implementation and do not become more aware of Apple’s standard non-conformance as a result.
A non-commercial website oriented towards developers, or indeed a joke such as in this case, is fine, of course.
In short, violating open standards—bad, taking a stance—good, hurting regular users and business—bad.
The other one is probably just trying to be cheeky :)