Your specific situation isn’t addressed in the regulation or commentary. 1026.20(d) does state:
Initial rate adjustment. The creditor, assignee, or servicer of an adjustable-rate mortgage shall provide consumers with disclosures, as described in this paragraph (d), in connection with the initial interest rate adjustment pursuant to the loan contract.
It seems to me your initial rate adjustment per your contract has already passed before the effective date and as a result you wouldn’t need to send the 1026.20(d) notice.