IMO Apple and Valve are taking the opposite approaches but on a different axis than the article discusses: Apple is continuing to increase their lock in and remove choice, while Valve continues to add choice. You can argue that Steam being a nigh-monopoly means there isn't a lot of choice, but I'd argue that's not correct. For one, Steam rarely censors games (it does happen! A notable case happened this month! But it happens rarely) and doesn't have requirements for games to use Steam's platform technology to be on the market. In fact, you're allowed to offer direct competitors to Steam features in your game without penalty (some games I play have both Steam Workshop support and the game dev's own mod platform support). For another Steam doesn't try to nudge you towards their solutions constantly either (eg like in the recent article on passkeys where the user had to click half a dozen times to not use Touch ID with the Touch ID option being on every page of those clicks). And of course, there's the "Add a non-Steam game or app" button in Steam that just asks you "where's the executable" and then it gets all the non-platform features Steam offers, like the overlay, screenshots, Steam Input (I think it even supports community input profiles for non-Steam games; I'm pretty sure I've seen community profiles for Primehack on my Steam Deck), etc. Of course the Steam Deck (and now Steam Machine and Steam Frame) are constantly advertised as "it's just a PC and you can do whatever you want with it". There's no lock in; you can install competitors' stores on those devices easily.
The reverse playbook then is that Apple is trying to make every option other than staying in the Apple ecosystem a bad choice, while Valve is trying to make Steam the best option in every scenario. The difference in base philosophy is the important part.
(Of course as a profit-seeking corporation there's no guarantee they'll stay this way, particularly after gaben leaves, but I'll appreciate it while it's here at least.)