It's not the idea that he prefers topping that's unrealistic, although it's true that switching is way more common irl than yaoi would have us believe. It's the way he described being on the bottom as losing something "as a man" that's not realistic, coming from a gay man. It's insulting to men who prefer bottoming, for one thing. Straight people insult gay people like that often enough, most gay people know better.
To me, in this context at least, when he says "as a man" its more of having Tamaki think of him as a woman. Seeing as Tamaki is straight Ioroi wants Tamaki to know he is a man, that they are equal as men.
Maybe its just because its a common thing in yaoi, having the gay man bottom for the straight man and feeling like the straight man might not see them as just as much of a man.
That and Ioroi just perfers to top. (Or at least has to trust who he bottoms for.) Thats just the feeling I got at least.
It would seriously be nice if I could feel the same as you about it! I wish it was a translating error (I'm sure it's not) and Ioroi actually thought "I feel like he wouldn't take this seriously if I had been the bottom" or something along those lines. But even re-reading, I don't get that vibe. Especially because he's a bit "I can't believe I thought about letting him do me" etc. It feels to me more like the mangaka sees it as a "normal" way for people - even gay men - to think about the top/bottom/switch thing. Which is quite common in yaoi but is unrealistic and also makes me sad.
It ruined the afterglow of their first time together for me, I'm not gonna lie! But hopefully it's just a hiccup and the rest of the manga is as great as it was up until that moment (￣∇￣")
(Or at least has to trust who he bottoms for) - aaah, that makes me hope beyond hope for a Sojou No Koi Wa Nido Haneru situation, "People who've been on the bottom make the best tops" and switching! But Ioroi has Sagami-sensei's standard seme facial features, so I kind of doubt it was ever going to be otherwise
Even in real life eryone has his own preference, not all gay men take turn so don't think that's realistic or something. If he prefers topping only, let him be. Both of them had their chance to choose what they were going to do. Ioroi didn't force Tamaki-san into sex, he let him go and Tamaki-san went back on his own after making his own decision. Isn't that good enough?
The "taking turns is more realistic" just bugs me too much.