Julia Evans has posted a list of
confusing Git terms and behavior along with explanations of what is
actually going on.

“Your branch is up to date with ‘origin/main’”

This message seems straightforward – it’s saying that your main branch is
up to date with the origin!

But it’s actually a little misleading. You might think that this means that
your main branch is up to date. It doesn’t. What it actually means is – if
you last ran git fetch or git pull 5 days ago, then your main branch is up
to date with all the changes as of 5 days ago.

So if you don’t realize that, it can give you a false sense of security.

Source: LWN.net – Evans: Confusing git terminology