Without knowing the full facts, it is not reasonable to criticise CHEM ENG instructor. As it is unlikely that you will hear the other side of the story, let me speculate what might have happened.
After a series of flights the CPL instructor spoke with the CFI about the lack of progress which the customer was making.
A decision was made to inform the customer that the rate of progress was so poor, that there was not a reasonable prospect of him succeeding even with additional support.
I would suggest that this course of action is better than stringing the customer along, extracting his hard earned money, only to be told much later than really he is wasting his time.
The news is clearly what the customer did not want to hear. It never is. But at the end of the day, this experienced instructor was giving his opinion. It is up to the customer to seek a second opinion, but reading between the lines, I am not terribly optermistic as to what that might be.
FOR THE AVOIDANCE OF DOUBT, I HAVE NO KNOWLEDGE OF THIS SITUATION APART FROM WHAT APPEARS IN THIS THREAD.