They do not use it on their 5.56 rifles, they are designated M-15's.
https://armalite.com/product-category/complete-firearms/m-15/
Even there second line Eagle product in 5.56 does not, they are Eagle-15's
https://armalite.com/shop/eagle-15-2/
Now on the rest of their rifles in other calibers they use AR, this is obviously something to do with how that lawsuit was decided, must be a caliber specific thing. Are other makers actually using AR to designate a rifle or is it just the community calling them that?