You can still bring it up to them as a problem that you have noticed where "some people" get overeager and interrupt others. mention the downsides and ask if he can help change the culture. You don't have to point the finger at him and it helps to enlist his help rather than complain.
You can try, but unless they (perhaps privately) realize they're part of the problem, I expect they'll end up verbally condemning interruptions while sabotaging any real attempts to curtail it, largely but not entirely by continuing to set a bad example. Is there a way to make this strategy actually work? By which I mean, have people actually seen it work in the long term? I'd love to be proven wrong.
It depends on their relationship, and the workplace and overall culture they grew up in. For various reasons, not everyone will be comfortable directly pointing out a flaw in their own boss.
I'd say that without knowing more, it's better to advise the safer and more diplomatic approach.
It is totally possible that beeing direct leads to the polar opposite of the intended result. This is something that can happen and it entirely depends on the people involved.
So some of use have learned how to recognize that type of situation and how to deliver bitter pills of truth without risking a job you might otherwise really like for it.
Be direct if you can, but don’t stay silent if you can’t.
