I'm really failing to see the distinction here.
Big tech will simply declare that phones aren't "general purpose computers". There is no reasonable endgame here in which: (a) this is enforced against cellphones and (b) this is not enforced against game consoles and (c) the EU doesn't end up looking completely ridiculous and arbitrary.
I'm betting that they cave on (b). It's the least painful option. The EU is going to have to enforce this against game consoles in order to be taken seriously.
It's hardly the same thing. Some services are not even available on a traditional computer FinTech started as mobile apps and they added website support later. It's stupid but that's how things are, the majority has chosen...
I'd expect the online stores on those consoles, and the resale of digital content, to be impacted well before running other OSs on consoles that didn't ship with that feature.
(personally I'd totally support regulation opening up game consoles, but they are fairly insignificant compared to mobiles)
That said, if Sony falls under the DMA, they may need to allow sideloading apps or 3rd party stores.