Here’s favorite/star flow on Macnchrome.
Edit Icon opens wp-admin in new-tab-window, thus forking flow.
Here are the site pickers with one site starred.
Here they are with seven sites.
Favorite sites starts to break down once non-favorite sites are pushed below the fold. Notice how the current site in the pencil icon site picker is pushed out of sight in the shot above. Contrast this with Recent Sites, which keeps the most recently used sites up top with the current site at the very top. I find that particularly useful in the pencil icon picker. This makes for nice chain publishing flow that keeps me on track. Favorite sites, by contrast, keeps the primary site at the top and pushes recent sites that are not favorited below the fold.
I like favorite sites, but not if it means pushing the current, most recently used site down, particularly in the pencil icon picker where recent sites flow currently feels really good. If the primary site is going to be parked at the top of the site picker lists, Calypso needs a way of changing the primary.