Excluding on part of otherwise excludable employees in ADP testing?

Hi all! I wanted to ask is this possible. If a plan has a lower minimum age/participation than 410(a)(1)(A), for ADP testing, the plan can exclude employees who are covered under the plan's lower minimum requirements but have not met the 410(a)(1)(A) minimums. Could the plan instead choose to exclude only a part of those employees?

Say the plan allows entry at 3 months participation and 21 years old, thereby allowing participation in the plan 9 months before required under 401(a)(1)(A). For 410(b) testing, could the plan exclude only the employees between 3-6 months participation while including those with 6+ months?

This sounds like you're hoping to apply the flexibility allowed for top paid group determinations, but I don't believe that's provided for in the coverage rules. 

The only leeway I've seen on that one is when you fall back on the plan's entry dates under liberalized eligibility, as opposed to the straight reading of the rule (where you go six months out from the one year anniversary, even if the plan had dual eligibility and someone snuck in July 1 even if it that were earlier than statutorily required).

The regulations only provide for permissive disaggregation of otherwise excludable employees using the maximum permissible age and service requirements of age 21 and 1 year of service.