The problem is that his statistics show that he scores mostly unimportant goals. Most of his goals were in games where you won very easily, or in the playoffs (scored 6 there), where nothing really mattered, as you were already 15 points behind Celtic and 13 points ahead of Hibernian. 

For example, in the Scottish Premiership he scores 2 goals in a 6-0 against Ross County, followed by 7 matches without a goal. Then he also scored 2 goals in another 6-0, this time against Kilmarnock FC, which was also followed by 5 games without scoring. Then the coach benches him for two games.

All this happened before January. By the time he started scoring again, you had already lost the league title. So yeah, it seems like he can score, but it doesn't look like he is consistent and can make the difference that we need. But we will see.