There is no need. It's a different type of muscle memory.
I've been learning to use a split ortholinear keyboard, and it exercises a different type of muscle memory than a regular keyboard, which is even different than on-screen keyboards. I have a different layout in each and I haven't lost any speed whatsoever.
I have been typing Dvorak for about 15 years, give or take (I had been typing qwerty before that). A couple of years after the switch I started to play World of Warcraft, and I thought it was too much effort to rebind all the keys (they assumed qwerty), so I just played it on qwerty. My brain quickly learned to associate the game with the keyboard layout, so I would type qwerty at full speed when chatting in-game. Typing qwerty on someone else's computer was much harder and required some conscious effort. I wonder if mentally switching between keyboard layouts is similar to switching between speaking different languages.
This is an interesting anecdote. Despite a longtime interest, I've been hesitant to bother trying alternative keyboard layouts because even with only really minor changes to shortcuts (capslock replaced with ctrl, emacs text navigation bindings for all apps) typing on an unfamiliar computer is almost comically bad, but I have gotten used to specific apps that don't play nice with my bindings (I'm looking at you Github text boxes stealing ctrl+e!).
It does seem to require some mental "switch" or trick. If I look at the keyboard (assuming it's got QWERTY on the keycaps, which all of my keyboards have had), it "reminds" me to type QWERTY and I can do it. It's not really full-speed or facile but it's good enough and it's not hunt-and-peck, anyway. If I look away, I cannot type QWERTY.
I picked up dvorak over summer vacation in high school because I was having bad wrist pain. My high school wouldn't let me use dvorak, so I painfully had to re-rewire my brain for qwerty in our high school labs.
I quickly realized that my brain would use dvorak for my mechanical keyboard at home but would only use qwerty on the soft keyboards at school.
I have an en-Intl Macbook that I work on personal projects on, and a Swedish Macbook for work. I find that I can swap between them fairly trivially, but as soon as I open Slack on my personal machine to quickly respond to a work query I’m completely at sea.
I wouldn’t be so sure. I (a QWERTY user) remember picking up my first phone with a non-numeric keyboard (Nokia E63, a Symbian-based QWERTY-keyboard phone) and instantly starting typing with my thumbs virtually blindly. I expected a long learning period; there wasn’t.
