Exactly. So, he can save himself the time and apply for the new one NOW.
You cannot impose your "logic" on CIC, because you don't know if they will accept the 4 month old certificate. According to CIC's stated policy, it is not valid if it is more than 3 months old when they get your application, so if they reject his application, he cannot argue with them about it, can he? So, rather than waste time hoping that they allow his application although he is submitting an invalid PCC, he can apply for a new one and advise them that he is doing so.
Again, your opinion and your "logic" are not binding on CIC. CIC's rules bind CIC. Don't assume you know what they will and will not accept, just do things as they say you should. Maybe that's not logical to you, but it is to me. *shrugs*
. I will wait till I hear something from them..