I agree with HOOTERS and Nait. If he's just delivering veggies, and he's pretty sure that he thinks that someone is home, I would imagine that he might get pretty annoyed at the thought of having to have to come back again later to deliver them when someone decides to open the door for him. Trying to open the door isn't right though, unless he thinks that because he knows your uncle he feels that it's safe enough for him to try to open the door to see if he could leave the veggies inside in order to save himself the trouble of having to come back.

Maybe you can speak to your uncle about him if he really bothers you. Would your uncle hire someone who might be dangerous?