The thing I find with the upstairs business lounge on this aircraft is that it's actually kind of small.
I've tried to visit there a couple of times now during a flight. Each time there has already been someone sitting there so I've turned around and gone back to my seat.
It sort of feels like you went and sat down with someone already there you'd be invading their space or forcing some sort of social interaction upon them.
I know this is strange given that you sit much closer to random pax in other parts of the aircraft, but that's just the vibe I've gotten each time I've tried to use the area.
I think the cause of this is the wall directly opposite (see below). If somehow it was able to not exist the space might seem more open & less like you're squeezing into someone's bunker or cubby house.