I realized that BLUFOR/OPFOR riflemen (heavy gunner in my case) assets refuse to attack an unarmed AAF strider (I did set the AAF as hostile to everyone).

In contrast, the blufor heavy gunners can attack an unarmed OPFOR Ifrit, and OPFOR heavy gunners can attack a BLUFOR Hunter. Only the Strider seems to be exempt from this kind of hostility.

I also thought that the soldiers hadn't been attacking the Strider the same reason they don't attack an MBT (since their weapons would be innefective towards it) but upon some testing, i found out that Strider has roughly the same amount of armor compared to its BLUFOR and OPFOR counterparts.