Source? If you made old.reddit.com the default layout, how many users do you think would go through the same trouble to use the new.reddit.com layout?
When they first launched the new interface some new users got the new one and some new users got the old one. The bounce rate for the new one was lower and the signup rate was higher.
You are not normal. Even the fact that you are likely consuming this website on a computer with its own keyboard, is not as common as it might seem if you surround yourself with other software developers. What you want, and what the majority wants are not the same thing.
As it happens I am an old.reddit.com dinosaur that finds your argument plausible, but I'm interested to see the data as well.
If you want to be guilty of something, I'd say it was approaching the conversation adversarially rather than charitably. "You were asked for a source" treats the other commenter as an inattentive schoolboy, and coming from a place of curiosity with a question like "But how do you know that's actually what happens?" might have done the job just as well.
I wouldn’t be surprised if me reading a thread with all its 200 comments on the old version and then leaving the site is considered bouncing, whereas me reading a thread (or rather the 20 comments on the thread you make available) and then accidentally closing the thread to return to the subreddit on the new version is considered successful retention.