That would require physical access to my phone, and access to the content on it, vs convincing a telephone company to transfer my cell number to a different sim. I'm less concerned about the former.
He said he’s currently using SMS so it’s natural to back-track your question to SMS based 2FA. The reason he wants to use app-based could very well be the one stated above - because the [main] alternative is easy to hack remotely, and that required physical proximity is a feature in this case.
