The latest Xbox and PlayStation are literally just AMD PCs that support connecting a keyboard and mouse if you have one (and the Xbox running a locked down version of Windows ripe with APIs explicitly made to have general purpose apps run without rewrite from standard Windows even!) - the only thing not making them a general purpose computing device is the restrictions on what you can run. That the restrictions don't let you run general purpose computing isn't reasoning on why the restrictions are okay to be there in the first place.

Now one could argue the intent is they not be general purpose devices, but so could the intent of anyone not wanting competing stores. I'm not sure the intent of how manufacturers want users to use it factors in as such.

One argument that comes up often related to this set is consoles are sold at a loss (and iPhones are not) on the assumption profitability (not increased profits) will be made through purchases on the platform. This is more of an bona fide difference between phones and consoles but has it's own debate as well (which I'm not going to get into here as this is already veering pretty far off the article topic).