Schedule MEP

401(k) plan is closed MEP.  Two employers share common ownership, but not sufficient to be related group. A 401(k) is not a pension plan. I don't see that the Schedule MEP should be filed for a 401(k) plan.  I assume that plan sponsor should attached the same schedule that applied prior to 2023. 

Am I missing something? Thank you for any guidance.         

The 2023 instructions to the Form 5500 page 3 includes the following definition:

Pension Benefit Plan

All pension benefit plans covered by ERISA must file an annual return/report except as provided in this section. The return/ report must be filed whether or not the plan is “tax-qualified,” benefits no longer accrue, contributions were not made this plan year, or contributions are no longer made. Pension benefit plans required to file include both defined benefit plans and defined contribution plans.

      The following are among the pension benefit plans for which a return/report must be filed.

      1. Profit-sharing plans, stock bonus plans, money purchase plans, 401(k) plans, etc. ...

For purposes of the Form 5500, the term pension is used to distinguish a retirement plan from a welfare benefit plan.

Thank you.