Well it's in the last line : Ideally, all members could be on the email list, rather than on the trusted list, so they could see activity feeds.
Already asked if someone could explain how to get all members invited/ added to the email list without adding members to the trusted list of the project profile, so hope we'll know the answer soon. I found some info (added that to the other question Philip asked , and tried to figure it out at the Project acount googlegroup , but it's not as easy as it sounds, we didn't set up the acount /group ourselves, guess when you set it up you can add all members to the mailinglist and invite them immediately or something ...
And of course at the top of that page it says : This is relatively new and still rough. We need more Leaders to experiment with them and help establish best practices. Please post questions and issues for discussion on the Leaders e-mail list. -- Whitten-1 11:43, 9 September 2015 (EDT)
So we're all still learning what's the best way to use the project profiles , it's still in progress ;)