I as a manager join the stand up, and I offer to the team the things I am working on and the blockers I am dealing with, just like everyone else in the standup. Maybe it makes more sense for me because as a manager I have a little bit of dev work that happens as well which is maybe just a culture thing at my work place. I can see how it would be detrimental to join standup and be seen as an auditor of all the things that the team is working on.
It is slightly different if the manager is also a developer, in which case they also have blockers to report. We have scrum masters to deal with blockers. They are not management, just one of the developers most of the time although I have had dedicated scrum masters in the past. The crucial thing is to make the standup a safe space for devs to openly discuss problems without their line manager breathing down their necks. The other thing management tend to do in stand ups is to use the time for irrelevant announcements, most of which should have been an email.
