It's always been a bit hit or miss whether it hits the limits imposed by GitHub. Backend adjustments and/or server load might have an impact. I also vaguely recall some mention of GH staff manually adjusting the limits for specific notable files (i.e. this one) before.
Ideally, they'd be at https://doc.rust-lang.org/1.74.1/releases.html, but the change adding release notes to the docs tarball hasn't actually landed in 1.74's branch, and wasn't backported.