Thanks to Gideon Brontë, I finally figured out how to make G+ sort posts by date and show all posts instead of just highlights (how stupid that it doesn’t do this by default, or at least have an option…). It turns out that only the “All” stream has this cherry-picking problem. If you view just a single circle, it shows all posts in the right order. So here’s my workaround:
1) create a new circle (I called mine “Everyone”)
2) before adding anyone to this circle, perhaps make it private (Profile > Circles > Edit, uncheck from publicly visible circles)
3) for each circle you have, select all and drag to this new circle. If you follow more than 450 people, this may take multiple days due to rate-limiting.
* when you go to Home, click Everyone (the default is All)
* when you add someone new, remember to put them in Everyone