Maybe, but would he really know that? Presumably the only time he experienced SSJ2 was against Cell. He made it sound like he truly did nothing for training during the 7 year gap. Would he have enough of a grasp on SSJ2 to know that it would be a weakness for him? Also he planned to fight with it in the Budokai and never made it seem like it would hinder him.
There's multiple reasons I can see for this. First, Goku states to Future Trunks that he had to work at controlling SSJ after first transforming (you'll have to correct me of the exact phrasing). If Gohan truly only transformed that single time, the long stretch of seven years with no training, fighting or thought of fighting would account for that. SSJ took all the way until the Cell Games to truly even master, and that was including years of training in ROSAT.
There's that, and Gohan's reoccurring performance anxiety and his lack of rage. He freezes up when it's time to fight and he always needed to be pushed into anger, and it takes a lot of prodding. I guess a lame analogy would practicing a backflip until you get it right, only to wait over half a decade, not even excising, and trying to do it again on the first or second try.
Hell, we can see this play out in FnF when he wasn't even sure he could go SSJ, and his Mystic form had melted away like a wet turd despite having done it in BoG, much less time that seven years.
