Yes, it can be confusing. I guess the question could be:
If I put on this link, and the link is and ad, and it makes me money, am I doing it for users?
In this case the answer would be "no" and Google wants such link nofollowed.
On the other hand, if this is the link for your users, you genuinly want to give them more info, then there should be no need to nofollow such link.
Could there is a darker undertone here in controlling links in this way that will make other search engines less effective?
Are wondering whether, now that Google has many other signals perhaps through visitor engagement, their motive is to have as many links as possible nofollowed, so that links makes other search engine algos less effective?
I do not believe this is the reason - and lets try not to go into conspiracy theories. Further, other search engines have choice to ignore nofollow or to selectively ignore nofollow in their algos.