Code J is for a regular distribution which would correct an excess contribution after the due date of the tax return for the year for which the contribution was made. This eliminates the excess-contribution penalty for the year in which the distribution is made and beyond.
Codes J and P together would be for a distribution that is a return of contribution before the due date of the tax return for the year for which the contribution was made. This makes it as though the contribution that is returned was never contributed to begin with.
Because the corrective distribution for your 2021 excess contribution was made in 2023, well after the (extended) due date of your 2021 tax return, the excess must be corrected with a code-J distribution of exactly the amount of the excess, with no adjustment for investment gain or loss. This will go on your 2023 tax return on Form 5329 line 20 to eliminate the excess for 2023 and beyond, but not for 2021 or 2022.
