Yeah, it’s entirely possible that some effect like that would confound everything too much. Bilinguals with close to equal proficiency in both languages might be less inclined to do some sort of mental translation, though. (Still, the whole idea comes perilously close to wanting people to “think in” a particular one of their languages, which in my opinion doesn’t necessarily make sense at all.)
Yeah, it’s entirely possible that some effect like that would confound everything too much. Bilinguals with close to equal proficiency in both languages might be less inclined to do some sort of mental translation, though. (Still, the whole idea comes perilously close to wanting people to “think in” a particular one of their languages, which in my opinion doesn’t necessarily make sense at all.)