Its not about them being shy, I am sure you seen the pictures or video on them in room on cam with her giving him a blowjob. They openly did it on cam and were aware being watched sense day 1. Them choosing to do it on balcony but she allows people to hear her moan,etc defin shows she isn't shy.
So its either 1 of 2 things, the couple monitors the thread and would like to surprise everyone when they have hard sex, and play hard to get for viewers.
Other option is I know this personally some people don't like having sex in normal areas, bed/couch/bathroom. and prefer it outside, in cars, on a balcony,etc. From my experience sex on a balcony with the wind blowing is nice with the right sunlight. Gives you a different feeling.
But that's just my 2 cents
ps. from what I read rlc doesn't mention anywhere "must have sex" it just says how it shows peoples daily lives and how its common to see them fight, argue, and yes have sex. But says nothing of requirements. So all they really have to do is be there majority of the month and live as a couple >_>