Don't get it wrong, it's not. In your opinion maybe it is, but no. For me, it's like their brotherly come back, supporting each other once again like in the past to bring Yona back, and there's no deep secrets at all. They're talking about what happened in the past, and Soo-won already knew that Hak knows about his secret. Soo-won confessing about how he really feel is like him being grateful that no matter what sins he did, bestfriends will always be bestfriends. Them talking without any hatred nor sadness just points out that they'll always be the friends they used to back then. (No hate, just stating my opinion.)
The symbolism meaning the show of intimacy between them even though they’ve been estranged. But do imagine if this same scene was between Hak and Yona. Hak taking off Yona’s armor to symbolize him talking to her on a more personal level without their class status coming into play. That scene probably would be read as romantic, because it is a show of trust and a very intimate act. So it does not have to be romantic I was exaggerating that aspect.
An intimate armor removing scene to symbolize having a conversation on the same level, where some of the deepest secrets are confessed, all contained in a pair doomed by the narrative pair of childhood friends turned enemies????? HOMOEROTIC!