FWIW it really isn't that hard on Android, as you can just install Termux and then install stuff like clang or the Android SDK tooling. For a while a couple years ago I was doing this and using a foldable bluetooth keyboard; the setup was small enough to fit in my jacket pocket and felt a bit more convenient than carrying around a laptop.
It's gotten to the ridiculous state where common phones will very often have more screen resolution than 14'' laptops. So as long as you have a way to comfortably stand close enough you won't be lacking for pixels. Eye strain from focusing that close will probably be higher though.
This is clearly an extreme case, and quite impressive. I was commenting on the general case of developing on a phone screen. 2300x1080 phone screens are now on ~200$ phones, while getting more than 1920x1080 on a 14'' laptop is difficult and gets you a "why would you even want more than FHD on a 14'' laptop" comment consistently. At least 16:10 is now becoming more common so 1920x1200 is growing a bit.
actually working on tiny screen is not that hard tbh. When my macbook was under repair I used to use microsoft rdp to connect to other pc.
The good thing is i can use external keyboard and mouse. And screen was somewhat okay. The only issue was battery as I keyboard + mouse drains battery a lot.
I tried this and it was a bit of a pain. Partly because the device didn't have enough storage, but stuff like finding a decent editor was hard, and just about everything needs some tweak to work.
My experience is not that bad. It's Linux after all, of course you're gonna need to tweak something. I spent a few hours customizing Neovim with Coc.nvim and were off to go.
It's kinda crazy that Termux on my phone runs smoother than any terminal on my laptop. (TBF it does have more RAM and faster storage!)
Apple doesn't advertise much outside the United States, and given Android is significantly more developer friendly, there isn't a reason for a student to learn on iOS.
Android's pretty plug and play in that regard thanks to USB OTG, and you've got a lot of the Linux world amenities on top of it (especially if you're rooted).
Kudos to him. If he was able to do that, then development shouldn't put up much barriers anymore.
I would totally buy him a decent PC though.