It's pretty common for Koreans to still use honorifics even if they're already dating. Plus he's literally Suha's boss so maybe he finds it more awkward to call him informally.
PLEASEEEE IF I SEE THE YAOI TAG TURN INTO SHOUNEN AI . ALSO LMFAOOOO SHE SAID BBQ AND LEMON PAPER I WAS LIKE ISNT THERE MORE FLAVOURS NO IM JUST DUMB THINKING ABOUT WINGS
Currently there are only 4 chapters of the fans translations and they will update soon. The fan translations are closer to the Korean story. For more information read fan translations chapter 41 page 1.
tbh his friend annoying like why you in his business