The avatar shown in the newsfeed is the avatar of the user who pushed the commits, not the author of said commits (of which there can be many).
So the two pages do not show the same kind of information. The commits page shows individual commits, unrelated to how, or by who they were pushed, while the newsfeed shows the "events" that have occurred on the repo.
Making commits is not done on the site, but locally in a developer's clone. The event that makes those commits appear on Bitbucket is a "push" and so that's what the newsfeed depicts.