Can bananas really be ripened through oven baking? I am following a diet for IBS called the Specific Carbohydrate Diet (SCD). 
Only bananas that are ripe, i.e. well spotted, can be consumed. Green and non-spotty can not be due to a difference in sugars. 

I've seen a few posts on facebook saying that bananas can be ripened simply through baking them in the oven.

Does this really lead to the same change and resulting sugars as a ripe banana?
No. Ripening is a specific chemical process. Baking the bananas has a similar effect in sweetening the fruit, but it is not the same as ripening, which is a process which occurs after exposure to ethylene gas (in a supermarket banana at least). Given that your diet seems very specific about the carbohydrates, I wouldn't diverge from its recommendations.