Check out the following article
https://ferenczylaw.com/article-defined-benefit-plans-determining-professional-status-of-plan-sponsors-for-pbgc-coverage/
Section RULINGS WHERE THE PBGC FOUND THAT THE OWNER WAS A PROFESSIONAL
We spoke to a PBGC “higher up”, I believe a supervisor at the time, who initially balked at the question, and when we pushed for an answer, mentioned that a pharmacy where sundries were sold, more than 40% of the business revenue must be “phamacy related” in order not to be covered.
Applying for a PBGC coverage determination is a long and expensive process and we have seen responses of up to 6-8 months.
Of course the supervisor has now retired.
Hope this helps.