That's an interesting perspective on contract law, generally in which an agreement must be matched with consideration, otherwise it's only as good as good as a handshake. Where is the consideration? What did $IMMB receive for the transfer? Under the "agreement," $IMMB was to own 80% of $ENZC. Did that transaction ever happen? That, my friend, is the question that needs to be answered.
Because Harry was the majority owner and in control of IMMB - he had the authority to enter into an agreement with ENZC.
Which is how he transferred all of the assets into ENZC.
When you enter into an agreement its final. There is no "receipt" necessary.