You can stop looking for corrected W2, because your client missed the deadline. The employer has taken a valid position.

The 1099-R will be for the corrective distribution, so that will be 2024. The point of "timely" corrective distribution is to make the excess moot.

"I would file the return as is"

If it is done in time, then the excess is no longer excess. Otherwise, the excess deferral is taxable for 2023 and for the 2024 distribution. The earnings are taxable when distributed.

"Timely" means by April 15. He should contact them NOW.