You can find full programming environments that run on phones and i amused myself for some time while waiting for a friend at a coffee shop by writing a simple C program in Vim with Hacker's Keyboard and Termux.
But just because something it is technically possible it doesn't mean it suited for it.
My washing machine or Minecraft redstone blocks may be Turing complete, but realistically they are the best interface to express what the mind intends to express.
These are mostly used as Ipad apps, and even then, they nowhere provide the tools that are available on a standard PC. Sure, you can use them to do cool things, but I can also create paintings with just ketchup and fries. That's not what 99% of people who have fries in their hands do/should do.
Are we really going to make the case that Garageband and iMovie allow for "precise editing or manipulation of content"? Last time I used either, they were like watered-down versions of real software that railroaded you through different pre-made templates.
Wanna make music? Press the chord buttons to play a tone on the synthesizer preset that you can't modify!
Wanna edit video? Drag your clips into this timeline with 3 transition effects and a half-dozen compositing themes!
https://apps.apple.com/us/app/procreate-pocket/id916366645
https://apps.apple.com/us/app/garageband/id408709785
https://apps.apple.com/us/app/imovie/id377298193