My opinion;
1) If he "
does not get any pre or post flight briefing or even know the objectives of the particular flight" - then he needs to (a)demand a partial refund for the 12 hours he's flown, as pre and post flight briefs are a part of the package, and then (b) change instructors/flying schools;
or,
2)Re-assess himself and perhaps realise that he might NOT be "
a bright student" after all!
Yes, there is a certain amount of self-study that needs to be done before kicking the tyres and lighting the fires, however at the tender age of 12 hours, the Instructor's job also consists of holding the student's hand (metaphorically speaking), and walking him through the stuff to be covered.
Again, in my opinion, debriefs should be relatively short - probably 5-10 minutes max - as any corrective action should be pointed out at the time, and in most cases a pilot will realise,
at the time, that he has stuffed up..knowing how to avoid making the same mistake is what counts.
In answer to your question, "No".......the service SHOULD be part and parcel of that which has already been paid for, and for which the instructor is paid!