Hello mr. LEM,
1. If you were my captain, and I was PF... would you please call for a go around before you start "helping", so neither of us knows who is steering what?? That's about the basic of basics in the crew concept! If you would "help" me in case you expect my landing to turn out to be firm... we would end "am grünen Tisch", where you may try to explain why you didn't stick to SOP and therefore greatly endangered the flight.
2. If, on an A320, the captain decides to "help", the FO has a flashing green light in front of his nose, so he will notice. This captain you met when you sat on the jump was not telling the truth. My guess he tried to look like just a real true airman as you are (which he obviously is not).
3. Is it IYHO also possible for a captain to make a hard landing? Or do you think the FO is not capable of taking over controls and saving the day, when needed? Your question only refers to the captain take correcting action, I have seen many bad landings made by the LHS.
Regards,
P77