I just made a discovery.
When you go to try mode, the AAS bonus damage is indeed not applied to decoy.
The Decoy AI does not interact with minion waves as well … initially.
HOWEVER, here comes my discovery.
After you used B or respawned for the first time in a game (or try mode) , the effects start being applied.
Please see this image:
https://imgur.com/a/VJ7CKmV
It shows my AA + decoy’s damage to a minion it interacts with.