401(k) plan + SEP, and nondiscrimination testing

[AndrewZ]

Husband owns a company 100% that has a 401(k) plan with 1 non-NHCE. His wife has a SEP for her sole prop (she's the only employee). They're in a community property state, so the businesses are a controlled group.

I do know the SEP is required to cover all employees in the controlled group (which it's not), and be aggregated with the 401(k) plan for top heavy determination (and may not be allowed to co-exist with a qualified plan, depending on the SEP agreement). I'm pretty sure that SEPs are not subject to 410(b), BRFs, and 401(a)(4) testing (since a proper SEP would always automatically be non-discriminatory), and so the 401(k) plan does not have to be aggregated with it for testing. The 401(k) plan has a non-standardized document that doesn't cover other controlled group companies. So my understanding is that the 401(k) plan is not negatively impacted by the SEP or the other controlled group company.

Is this correct?

Thanks.