Safe Harbor 401k plan - basic match & discretionary match - catchup only

[Guest elirpa]

I have a Safe Harbor 401k plan with basic match. The plan also has a discretionary match with no accrual requirements that matches catchup contributions only.

I believe that 410b would pass since all participants would be eligible for the Safe Harbor Match - since no accrual requirements.

Regarding ACP - since the discretionary match is limited to catchup contributions only - is this an example of HCEs receving a higher rate of match than the NHCEs; and therefore an ACP test would be required for the discretionary match?