2023 retroactivity due to improper company match

401k plan match was provided in 2023 when participant wasn't yet eligible (90 day mark wasn't hit until Jan 2024). 
Participant has been advised that a year timeframe is when it was supposed to be corrected, they were advised that ERISA guidelines do in fact apply to ERCPS in this case, and that the timeframe for adjustments has passed.

Plan admin is advising that an “excess allocation” which must be corrected in accordance with section 6.06(2). An Excess Allocation is corrected in accordance with the Reduction of Account Balance Correction Method set forth in this paragraph. Under this method, the account balance of an employee who received an Excess Allocation is reduced by the Excess Allocation (adjusted for Earnings).

Who is right? 

And furthermore if the correction is to be made, is the proper method to pull distributed funds from the account immediately? 
 

3 hours ago, Kikka said:

Participant has been advised that a year timeframe is when it was supposed to be corrected

Advised by whom?

They didn't specify. 

That is an acceptable correction under EPCRS as far as I know. If a participant receives an allocation they were not entitled to under the plan due to an error, one way to correct it is to removed the funds from the participant's account, adjusted for gains/(losses) so the participant is in the same position they would have been had the error not occurred.