Man, I literally re read the chapter. There's no reference of the real name or that they know each other in Real Life. They talked about a game where the MC used a Korean nick.
Gilman never said he knew who that person was IRL, and if he knew he wouldn't have doubted MC intentions about going on voice for example.
Literally a good chunk of the plot wouldn't make any sense if they knew each other before.
You're reading too much into something, there's no "it's implied", it's not there therefore not real.
MC doesn't know ML but I think ML does know MC.
Chapter 14 when the friend called and asked him if he's comfortable ML coming to the wedding, the MC replied with basically "I don't him IRL" and the friend said "then why did he-?".
In my head that was ML asking if MC was comimg to the wedding too. He probably only came because he knew the groom and MC was acquainted. I just realized this is just my own speculation lmao, that was why I said it was implies that ML knew MC

THEY HAVE MET AND ALREADY KNOW THEIR NICK IN GAME!! LET'S GOO