I've met two people in the last 4 months who spent hours at work on the phone with their significant other. One was a guy working on our cable box. He was carrying on a running convo with his wife on his airpods about nothing really, while occasionally speaking to me. The other was a UPS driver I chatted with at work. He also said he has his wife on an open line on his earbuds while he drives and delivers. I could never. But apparently that's how some people roll.
In the case of the Proudfoots, I would find it disturbing if there's routinely an open line between Sebastian's mom and step-dad, since it also leaves Sebastian's life on an open line. Imo, Chris always has an opinion and is always willing to tell you. If that's a regular practice for them, it could be disruptive of Sebastian's relationship with his mother. It would be, imo. It could cause significant stress for S. He may not have the communication skills at 15 to express how he felt about that. I wish an interviewer would ask Seth if Sebastian said anything about it.