I have been approached in parking lots before in my city by guys saying exactly the same thing.
They either wanted to sell me a speaker or gave me a sob story about needing gas money. I never gave them any business or money and I didn't feel threatened.
I don't know how the (possible)BG was approaching and no weapon was pulled so who knows?
Yes, I have had exactly the same experience. The guy asked if he could talk and never approached within 75 feet? I've been in his position before asking for directions. I don't especially see the threat, but hey, nobody got hurt or anything, so it came out fine. If people were in the parking lot they might've thought you were a jerk, but you're not there to make friends. I don't see what you'd call the cops for though. To report that a large guy asked if he could talk to you?