As i mentioned above shove is not a normal standard action since it has to interact with the attack action in a way that no other action does. It is not simply changing from BA to action.
If they cannot do it, do not want to do it or just think it is too much effort for that change remains speculative.
Shove interacts with the attack action in the exact same way that the attack action works, and Larian has already gotten the attack action (specifically, Extra Attack) to work in BG3. Thus, they could get the Shove action to work properly by having it cost the same resource as an attack.
