The Alpine is also the only car with a low rear cooling outlet. The other cars raise it and shrinkwrap the bodywork around the gearbox (like here on the Toro Rosso for example)
So it seems the other teams wanted to clear that path toward the diffuser top/beam wing bottom as much as possible, whereas Alpine seems to have scarified it a bit (that path is fairly cluttered with all those suspension arms anyway) and cleared the top of the beam wing instead.
It's visible here too. It's clear how Alpine is using its "unnecessarily" wide and humpy rear bodywork to actively orientate the airflow towards specific areas, and probably to attract some of top flow downwards. #downwash
https://www.flickr.com/photos/jonmcclin ... 0299877691