I've heard before that you want to make sure that your ratio of unfollowed to followed links looks good and natural so that your links "look natural". Only when you make such a statement does it mean that your link ratio of followed and unfollowed links is not natural.
Google's John Mueller said "that's not true" when asked about it. The question was, "It is ideally recommended to have a good balance between the follow links and the no-follow links. This helps us ensure that we are not hit by a Google penalty related to links."
Here are these tweets:
That is not true.
– 🍌 John 🍌 (@JohnMu) July 31, 2020
It is true that these link tools show a site distribution between followed and unfollowed links. So it makes sense why some SEOs are talking about it. I don't think I've ever looked at this metric before.
Forum discussion on Twitter.