As to the ground hot dog recipe, none of the restaurants in Flint use it. It originated with Joy Gallagher, Food Editor of the Flint Journal in the 1960s and 70s. She published a couple recipes, the ground hot dog recipe being one of them, while the other containing beef heart was considerably more accurate. Unfortunately, folklore grew considerably surrounding the ground hot dog recipe, and it was somehow attributed to Angelo’s. What I’ve collected about this fiasco, including scans of the articles over the decades, is available here.
The usage of beef heart is really what sets all three coney styles in Michigan apart from other coneys around the country, not just Flint. In a Metro Times interview with John Koegel published on June 27, 2007, Mr. Koegel specifically stated “Beef hearts are in our Koegel Detroit-style chili. National and Leo’s Coney Island and Kerby’s Coney Island use beef-heart products, though not ours.” In another Metro Times article by Michael Jackman dated February 18, 2014, Grace Keros, owner of the American Coney Island downtown and Canton locations, stated she owns the Detroit Chili Co. The Detroit Chili Co. sauce is available at GFS Marketplace stores, and the first ingredient listed is beef heart, meaning both American and Lafeyette use the meat in their sauces. Of course there is another Michigan style of Coney Dog in Jackson, developed by George Todoroff in 1914. In a piece by MLive’s Brad Flory on June 4, 2014, Richard Todoroff stated beef heart wasn’t in the original recipe. However, he followed this by saying “Coney restaurants in Jackson began using ground heart during World War II because it was easier to obtain than regular ground beef.”
And finally, earlier coney shops didn’t include what we see as “traditional” Greek dishes, and most of those stalwarts still don’t today. Contrary to popular belief, those dishes didn’t become part of the Greek culture until later, so Coney Islands that opened prior to about 1950 never included them on their menus. This includes Angelo’s in Flint (c. 1949) and Red Hots in Highland Park (c. 1921), while the menu for Keros’ American Coney Island (c. 1917) only includes a few such items.