I always add some jitter but never actually had a problem where it would have been relevant. Recently I added it to a project where others also see it (not just a hobby thingy but something at work) and I was wondering if it would look silly, like premature optimisation. I looked on Wikipedia for how established the practice is and it barely gets a sentence... with no reference.

Do you know of a documented instance where it would have helped?

Reminds me of this blog post I read yesterday, about Buildkite introducing jitter in their CI agent to reduce synchronisation

https://buildkite.engineering/sleeping-at-scale/