It's been very clear to me for quite awhile that they have to be doing this to push users to their mobile app, at least on iOS. I used to review PRs on my phone at night, but now I have to use the app because anything over a thousand lines will crash iOS Safari or cause scrolling to misbehave. Reddit has done the same over the years, as have countless other web apps.
You really can't escape the enshittification.