If you write an OS that can only run a single browser, and you do not publish APIs to let other browsers have the same performance as yours on the OS, the EU antitrust commission gets into action and quite energetically.
If you make a CPU+chipset that can only run a single OS, and you do not publish APIs that let competitors install at all, it is just fine.
And if you make a phone with a lock that make it work only with a single carrier the situation is intermediate, since it is OK, but you must guarantee that after a certain amount of time the user can unlock it.
I wonder if there is a line that lets one know in advance how cases would be dealt. For instance, if there were a TV set sold at a discount or at loss but refusing to play some channels how would the case be dealt with?