a good question, in fact, I would go so far as to say an excellent question.
I don't recall seeing an example like this written up anywhere.
You sound like the criminal mastermind on a Columbo mystery, worried, and thinking "I have the perfect crime to avoid top heavy. What am I missing?"
I think Dolly Parton was a special guest star....
so Detective Columbo shows up, runny nose, a cough, a sneeze...
"I'm thorry, but I have a bit of a code"
But the " Code" says (416(g)(2)(A)(ii)) "Required Aggregation - each plan of the employer which enables any plan described in subclause (I) [any plan with a key employee] to meet the requirements of section 401(a)(4) or 410"
now looking at the facts, if plan A only has the 2 owners, it has the key employees. But there are NHCEs. so in testing Plan A for coverage, it would fail testing because no NHCEs are benefiting (as opposed to there not being any NHCEs at all). Thus you have to aggregate for coverage to pass 410(b). But once you aggregate for 410, you have to aggregate for top heavy.
And of course, Columbo would conclude with "Got you!"