Critique of the 'husband as covering' concept; why was Aquila present?

Option 1 (complementarian 'covering' view): Mike is suspicious -- functionally what does 'covering' mean? It's vague and not clearly biblical. Option 2: Aquila was there because it would be inappropriate for Priscilla to be alone with Apollos culturally, but this makes Aquila just a 'spare tire' male escort. Option 3 (Mike's preference): both Aquila and Priscilla had important things to share with Apollos -- they both understood theology and both communicated it. This best fits the text ('they took him aside, they explained').