I don't find this to be true. At all. I use standard QWERTY on my Macbook. At my desk, I use an Ergodox (tented, split, columnar/matrix, thumb clusters, etc.) with a custom Dvorak-based layout. My job frequently requires I switch between desk and laptop usage. It's not a problem and not something I need to think about. My brain and hands just do what they need to do wherever I happen to be typing.

If anything, I think the opposite of your statement is true. The further away from the standard you get in your exotic preference, the easier it is to compartmentalize that layout, the easier it will be to switch as needed.

Not for me. I use a Kinesis Ergo Advantage at work and home, and have no problems using a standard QWERTY keyboard (infrequently). Switching requires no thought or practice.

The Advantage products shift the major keys where you would normally use your little finger on a QWERTY keyboard to your thumb. It is heaven.