Agreed. However, even under intense oppression, people can still be out and thrive against the machine. We actually see that with all the other gay characters in this story.
The very concept of "coming out" was pushed by Harvey Milk in the 70s at a time when sodomy laws were in effect in several parts of the US. Homophobia was rampant, as was police violence against trans people and visibly queer individuals, yet there were still thriving communities like the Tenderloin popping up. Milk argued that coming out pushed back against heteronormativity, broke down stereotypes, and would help to unite queer people everywhere. To add to your point, I think a lot of people have forgotten that coming out is as much a political statement as it is a personal one.
All that said, no one should feel pressured to come out, especially if they don't feel safe to do so; but, I think it's important that we all recall that standing up proudly together is the strongest path out of hetero tyranny. Garam coming out isn't going to solve homophobia in SK, but he will be able to live a much happier life and will find support in his friends/community. There will always be homophobes and hate (unfortunately), but that doesn't mean we have to bend to their expectations.
I don't think readers realize how intense the homophobia is in Korea irl