Did see one behavior I"ve not seen before though ... and it was present when the site was 2.9.4+ all the way through the 'moodle march'. When site admin clicked on any links in Site Admin menu, the menu did expand, and the center panel was also populated with the same links in the expanded menu. The center panel thang was the change to behavior observed in all other stock Moodle installs. Present in all themes that I checked. It's a minor thing (I hope).
Of course, I just might have overlooked some new setting also .. and hadn't discovered it ... yet.
'spirit of sharing', Ken