Colo your hardware, run open source software, and don't tie in to external services. Most mobile apps can be mobile-web optimized, as a fallback if App stores shut you out.
I like native apps mostly for their speed, but unless you're doing something requiring a sensor on the phone, mobile web can do it all.
Not quite. You can just move your hardware if something goes south. There is no proprietary magic sauce you are depending on from the colo. That's similar to saying everyone that uses electricity from the grid is sharecropping.
The use of the term in this context is calling out the specific vulnerability of using the walled gardens of Facebook/Google/Apple and the other behemoths. By your literal correctness of the term, there is no possible way to operate on the internet, since you don't own the land and the network cables from your servers to the clients.
Pulling one's head away from their rear end provides the vision that relying on specific vendor platforms, with their own goals and interests sometimes counter to yours, is different from using a colocation for servers.
I like native apps mostly for their speed, but unless you're doing something requiring a sensor on the phone, mobile web can do it all.