The problem with this line of reasoning is that said companies might not have even thought about trying to do something with those platforms because it was assumed impossible, and they didn't want to go through the effort of a court case to make it so. It's hard to say what would happen if consoles opened up without it actually happening.
> Point #2: ephemerality.
With how much mobile OSs change I'm not sure it's relevant. Apps that aren't kept up to date (esp. when it comes to changes in how the system manages privacy settings) tend to be delisted, and the rate at which those changes happen is much faster than the 7-10 year console cycles where backwards compatibility is a requirement even when major parts of the OS change (see: Win8 -> Win10 kernel transition in the early days of the X1). Admittedly, keeping up with mobile OS changes doesn't usually require a full rewrite of the app, but neither did anything moving from X1/PS4 to XSX/PS5.