I would word it this way: The regulations are as follows 1.401(k)-2(a) (iii) Special rule for early participation. If a cash or deferred arrangement provides that employees are eligible to participate before they have completed the minimum age and service requirements of section 410(a)(1)(A), and if the plan applies section 410(b)(4)(B) in determining whether the cash or deferred arrangement meets the requirements of section 410(b)(1), then in determining whether the arrangement meets the requirements under paragraph (a)(1) of this section, either—
(A) Pursuant to section 401(k)(3)(F), the ADP test is performed under the plan (determined without regard to disaggregation under § 1.410(b)-7©(3)), using the ADP for all eligible HCEs for the plan year and the ADP of eligible NHCEs for the applicable year, disregarding all NHCEs who have not met the minimum age and service requirements of section 410(a)(1)(A); or
(B) Pursuant to§ 1.401(k)-1(b)(4), the plan is disaggregated into separate plans and the ADP test is performed separately for all eligible employees who have completed the minimum age and service requirements of section 410(a)(1)(A) and for all eligible employees who have not completed the minimum age and service requirements of section 410(a)(1)(A).
In other words, you have a choice
1. All HCEs and only those NHCE who are not otherwise excludables (there is no reason to run an otherwise excludable test as their are no HCEs
2. Split the test into 2 - All who met 1 yr/age 21 and another test with all otherwise excludables (including OE HCEs) you have 2 tests, refunds in one test are not really related to refunds in another test.
can't speak for other software, but
Relius coding option 1 would be 'carve out' - you carve out all the HCEs and just those NHCEs who have met the 1 yr age 21
option 2 would be 'test separately' because you are indeed testing two groups separately
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by the way, there is no similar rule for purposes of Coverage