IMO AA is always an awsome store with great people, one of the best in new england.
Also, I get how 6 line advice can get confusing.
They are very often model reef tank citizens, but sometimes they get aggressive when they get big - hence the things you have read about them being a problem. IME, I have had two over about 4 yrs (lost one during an ICK treatment brought on by another fish), neither ever showed any aggression toward any other fish at all.
It gets confusing in the details on this particular fish - mike would not steer you wrong.
Don't worry about the 6 line at all, and if it does start to develop an attitude problem in a year or 3, send me a PM and I can loan you a fish trap to catch it.
Overall IMO AA is an A+++ store, don't get dismayed by conflicting opinions on 6 lines.