I've been using Dvorak layout exclusively on my computers for over 20 years and I totally agree with you, QWERTY is just a better option on a phone.
Some years ago, I set up my Android phone to use Dvorak layout but I quickly reverted to QWERTY, without being able to use my muscle memory, it was actually a very frustrating experience.
Because most Dvorak users do not use a keyboard labeled with the dvorak layout, you never really learn visually where the keys are and you only know the layout in your muscle memory which does not translate at all to using a touchscreen keyboard on a phone.
But wouldn't you use Dvorak with a larger device (so that you're typing on the on-screen keyboard conventionally) or that you use with an external keyboard? I use Android devices this way and until this story it honestly didn't occur to me that iOS wouldn't support the equivalent.
Some years ago, I set up my Android phone to use Dvorak layout but I quickly reverted to QWERTY, without being able to use my muscle memory, it was actually a very frustrating experience.
Because most Dvorak users do not use a keyboard labeled with the dvorak layout, you never really learn visually where the keys are and you only know the layout in your muscle memory which does not translate at all to using a touchscreen keyboard on a phone.