I'll try to be objective at this
This game against the bteam or cagliari means pretty much nothing. But its still a competitive game. Him scoring such a good will boost confidence.
Hopefully, this will make him more clinical and composed when facing the keeper in serious games.
Also, giovinco puts efford in each game. vucinic would have likely slept on the pitch the entire game cause cant be bothered with playing against that crap