I wonder if it's actually an indication of how unknown it is. Korean media is usually very precise with showing brands - if you can see a logo it's almost definitely product placement. Using a relatively unknown app allows them to avoid showing something recognizable.

This is just an idea though, I have no real basis for the claim. I have noticed the same thing, though.

They prominently displayed the line characters, Brown and Cony in a message chat between the two main characters in 2015s "Hyde Jekyll Me" on Netflix.

I doubt you'd do that as a mean to show a generic chat. I think that is more of an attempt to make inroads in Korea (or perhaps pandering to viewers outside Korea)