Not an uncommon situation.
I have flown with a lot of students after their official training finished.
Not necessarily because they needed it, most of the time just for the fun of it.
I think the instructor is blamed here, don't agree with it.
His only mistake seems to have have been not to remind you how to log it properly.
Yes, you have not logged it properly. You were PIC, you should have logged it as such without adding the dual received bit.
What I don't understand is as to how you were able to do the skill test without the examiner reviewing your hours logged.
As far as advise is concerned; fly the 50 hours.