That's awesome when a simple swap wins over the crowd. So many people are suspicious of plant-based stuff until they actually taste it. Getting the grill guy curious is a huge win, like you changed one mind right there. Sounds like your burgers just spoke for themselves.
Exactly, that initial curiosity is what breaks the ice. Once someone like the grill guy actually tries it and sees it holds up on the grill, the mental barrier starts to come down. It shifts from being a weird "imitation" to just another good option on the menu. Those small wins at a casual cookout can do more for changing minds than any big argument.
Ever think it's about the texture? Adam_patel is right about the grill making it real, but that good chew is what sells it. If it falls apart, people write it off.