Aggregation for ACP Only

Can two plans be aggregated for ACP testing, but not ADP testing?  (Note:  I'm using "plan" in the colloquial sense here.)

I understand the the 401(m) and 401(k) components of the plan are separate "plans" under 410(b), but Treas. Reg. 1.401(m)-1(b)(4)(iii) and (v) indicate that this treatment does not apply for purposes of permissive aggregation under the ACP testing rules.  I take that to mean that, if you aggregate plans for ACP purposes, you also have to aggregate them for ADP purposes.  However, I have found surprisingly little discussion on this topic thus far.