I had an interesting experience the other day. I have been using split keyboards for years, but only recently began using a Kinesis Advantage 360 Pro as my daily driver for work; I am so use to the layout now, that in instances where I have to use a non-split, or even my older splits, my fingers fail me entirely - like my brain forgot how to type, my thumbs eagerly searching for the thumb cluster that isn’t there.
I need to fix the position and angle of split keyboards. If the halves move too easily, I lose accuracy. Therefore I prefer non split keyboards. If they have angled halves that allow the wrists to be comfortable, that’s the best of both worlds for me.
I constantly switch between an ergo keyboard with Colemak DH and standard keyboards with QWERTY at work. Somehow they feel different enough that I can keep the muscle memories separate and switch easily.