Generally people just get larger phones instead of typing one fingered.
The awkwardness of phone coding isnt the typing of text (wherein most people rely on decent prediction rather than precise typing), it's the use of symbols.
I have a OnePlus 13, which has a nearly 7 inch screen. My two thumbs still block most of the keyboard. Do you know anything larger? I would get a folding phone but they are too fragile.
Not every programming languages require a lot of symbols. Like Python, Go, OCaml etc. For me writing many symbols is awkward even on a physical keyboard.
Also, using two thumbs can be more awkward if you have big hands.