Layout switchers have some bias here because they don’t type as well in QWERTY anymore or they didn’t touch type QWERTY.
When I'm writing something that doesn't require a lot of cognitive overhead (typically chatting online, when I may have a lot to say but it's not particularly intellectually demanding and doesn't require a lot of precision or proofreading) I can reach pretty high WPMs.
I'm not convinced that typing speed is always brain-bound outside of typing tests. If I'm telling you about my day at work I'm pretty sure I can just "stream-of-consciousness" directly through the keyboard with very little overhead, especially if I do it in my native French.
I was trying to talk about comfort difference between keyboard layouts anyhow, not the speed difference.
Given the same proficiency level of QWERTY and Dvorak/Colemak, comfort difference would be more noticeable for high intensity / little breaks / long duration activity like typing tests.
Are alternative keyboard layouts significantly more comfortable for practical tasks? I’m skeptical. (Most enthusiasts already agree they aren’t really faster).