I've reviewed CFR 1.402(g)-1 which provides the regulations on elective deferrals. It says:
A designated Roth contribution is treated as an excess deferral only to the extent that the total amount of designated Roth contributions for an individual exceeds the applicable limit for the taxable year or the designated Roth contributions are identified as excess deferrals and the individual receives a distribution of the excess deferrals and allocable income under paragraph (e)(2) or (e)(3) of this section.
This appears to imply that if the amount reported with code AA for 2022 is less than $20,500, the excess is in the traditional 401(k) rather than the Roth 401(k) account. I've changed my previous reply to reflect that. In that case, you can just include the $360 as miscellaneous income not already reported on a W-2. Still, the concern in not notifying the employer and taking corrective action is that the employer risks the 401(k) plan becoming disqualified, which could have substantial adverse tax consequences for everyone participating in the plan.
