iM@S DOES refer to the concept in a few songs besides (We Have a Dream and Zenryoku Idol both say hi, and in Zenryoku that's the primary focus)
Yes, that's true that there are other instances where Im@s refers to this concept. Those are good examples you brought up. I guess what I meant was that Im@s doesn't follow it completely 100% unlike other idol franchises. Of course, the only evidence I have to back up that statement is the fact that the producer can follow a close personal relationship (or in other cases fall in love) with the idols at least through the games (though some people tried to ship Touma and Haruka from the anime since they're from the same profession).
As you mentioned, this is probably easy due to the producer working behind the scenes and not apparent to everyone. In other idol franchises there are no ifs, ands, or buts about being in love. It doesn't matter if it's a producer, classmate, or another idol. There's no such thing as falling in love for those idols. At least Im@s has some leeway though it's restricted towards the producer only.
I believe in Uta no Prince sama there are instances of romance scenes with the idols and the main character, so Im@s isn't the only thing to break that barrier. Obviously, both franchises have a visual novel type appeal, so having the idols fall in love with the main character is normal. But, at least in my opinion that's better than not falling in love at all just because you're an idol.
fans actually finding out the idol is in love? That tends to be the larger issue I'm seeing here
I can see that as an obstacle (if they are like the JP fans). But, nearly all dialogue is between the idols and their producer and colleagues. So, I think the fans are not that important at least story-wise. Besides, by the time love happens it's already the end of the game, so we don't see that problem occuring.
After all, the forbidden thing is much more appealing.
That's true. It's kind of like the sibling love you see a lot in anime. Though, I personally wouldn't classify idols falling in love as forbidden, but that's my opinion.