There is no discussion here. I did the research so you don't have to.
they were AD when the picture was taken 04/19/2013.
read the WSJ article. no need to register as it explains it in the opening paragraphs.
you can check it for yourself. Wiki is a decent starting point.
you can do it all here:
"https://en.wikipedia.org/wiki/List_of_United_States_Marine_Corps_four-star_generals
check date of rank vs. retirement date, then figure out which generals fall into the same AD grouping.
Right now it looks like there are
4 3 active Marine 4-stars. Walters retired 10/04/2018
Link