It kind of matters during the time the story takes place because one, there is power over the student if they are dating a professor at the same college. The professor has power to effectively dismiss a student from the campus, and has been used in the past irl to force their students into an exploitative relationship. Two, the age gap is a potential power dynamic issue. Even if they meet as adults, it is ultimately a difference in mental age, financial power, and life experience the younger one may not have. All of these can be weaponized to harm a young person. Of course the characters may not be like that, but it is good to keep in mind why perpetuating these power dynamics in a ROMANCE manga is problematic especially a queer one. It's fair for people to draw a line at teacher-student relationship romance mangas
There's good things about the manga, but do please keep in mind why people criticize it. Not enough people separate fiction and reality
I'm well aware of the issues that can arise due to the age gap, as well as being professor and student (was it ever stated that they are in the same college course? I can't recall). What I didn't understand about the original comment was why them meeting for a short time 11 years prior is in itself problematic now. They've lived their own lives and grown up without the other. That the seme has held on to his feelings for years has nothing to do with the uke in this case. They are both adults. He interacted with the professor of his own free will, you can't just decide he has little to no accountability in what happens just because he's younger.
I think personally it has to do with the fact that the bottom had remembered and associated the top with when he was a child, and refered to him as boy in chapter 2 when he realizes he is falling for him. Plus, the bottom VIVIDLY remembers the time he spent with the top. Asking yourself the question would you fuck the neighborhood kid 10 years from now is what the person I think is getting at.
Also keep in mind that execution is key. We get in one chapter a wholesome thing about their past and the next chapter full on sex. My question is why are we putting a storyline about how they met when the top was a child when all of the romantic buildup and characterization of the top could also be done in a scenario where they first meet in college? That's my take lol

The art drew me in, but problematic tropes forced me to reevaluate. The younger seme and older uke dynamic, especially in student-teacher relationships, is a major turnoff for me. Attempting to subvert this issue, authors often make the older character the bottom, reducing them to teenage looking boy. The power dynamic is problematic when the seme met the uke when uke was a minor.