There are going to be instructors (and pilots) that do the right thing and there are going to be instructors (and pilots) that do the wrong thing. The instructor in the back logging PIC time is doing the wrong thing no matter how you slice it. It is not "professional."
Will it come back to haunt him?
Probably not.
Is it legal?
Maybe no, maybe yes, but doubtful!
It is not the intention of the regulation to log time while sitting in the back if you are the second flight instrutor but I've known pilots who flew through a wisp of a cloud and logged it as 1 hour IMC. What can you do?
The only thing you can do is control your own personal actions. Log the time you fly...honestly. THEN, when you go to the interview, you can say that you flew the hours that you said you flew and be proud of it. Stop worrying about the other guy. Worry about yourself and try to live within the FAR's as best you can. That is all anyone can ask.
To Your Flying Success...