I believe a grinder is heated/toasted. There was a deli near where I grew up in Philadelphia that sold grinders. They toasted something like a hoagie with cheese on top. The owners were from somewhere in New England. I’m not sure if that’s how a grinder is made tho. They made decent meatball sub and pizza, which is probably the only reason they stayed in business. They couldn’t make a hoagie or cheese steak to save their lives.
In 1967-68 when I was stationed in Philly there was a little hole-in-the-wall shop around Chestnut St and 13th Street off of Broad Street that had The absolute BEST Cheesesteak I ever had...
In fact, as far as I’m concerned, there is no cheesesteak outside of Philly....All others are imposters...