The thumb typing muscle memory does not translate to finger typing at all. Most Dvorak or Colemak users are comfortable using QWERTY on their phones. Clearflow really only works well with swipe.
No, not muscle memory, but at least the idea of knowing where keys are. I'd bet that non-qwerty typers mostly started with qwerty and possibly still need to use it on some occasions, so they remember.
I can't speak for everyone but I did an experiment to see if this was the case (I actually just wanted to switch to Colemak everywhere. But iOS doesn't support it natively and third party keyboard landscape is pretty bleak on iOS). I switched to Dvorak on my phone and got really comfortable with it. I was already comfortable with Colemak on my computer. Then I tried
1. Switching to Dvorak on my computer AND
2. Switching to Colemak on my phone
I already had a feeling that my Dvorak experience on phone wasn't gonna help typing in a physical keyboard and indeed that was the case. But also, the physical keyboard experience with Colemak didn't really help with thumb typing/swiping on the phone. On a physical keyboard, I can only type QWERTY at around 30WPM and Colemak at around 130WPM. However, on the phone QWERTY is my strongest layout (even when I can only type at around 50WPM with it).
Then there's the design philosophy. Colemak aggressively keeps the most used letters on the homerow. Paste a random Wikipedia article into this page and you'll see (https://www.patrick-wied.at/projects/heatmap-keyboard/ alternatively, here's the heatmap for the introduction to today's featured article about Augustus: https://postimg.cc/9RT8P4N6). On a phone this means that a lot of the times you'll be swiping back and forth horizontally. Resulting in identical swipe paths for a lot of common words.
And if Clearflow was ported to a physical keyboard, most of your fingers won't be doing any work and the active fingers will be doing weird tap dance. The position of spacebar (undoubtedly the most used key on the keyboard) to the sides where you'd be using your pinky would make it an RSI machine.
My point is that if you're comfortable with QWERTY on the phone, that's not because you're comfortable with QWERTY on the desktop. That's because you got used to QWERTY on the phone.