Cover a sheet pan with parchment paper or a nonstick mat. In a large bowl, stir together the all purpose (GF) flour, oat flour, baking powder, baking soda, sugar, and salt. Add in the cold shortening and using a pastry cutter or clean hands, combine the shortening into the flour mixture until crumbly.
In a medium bowl, whisk together the oat milk, white vinegar, egg, and vanilla extract. Pour this into the dry mixture, and stir with a wooden spoon until a dough forms. If the dough appears too dry, you can add a little more oat milk.
Lightly sprinkle some additional flour over the prepared sheet pan. Place the dough onto the prepared pan, and form into a disc. Don't overwork the dough here, but you can sprinkle on more flour if the dough is too sticky to work with. You want the disc to be about 1 ½ inches thick. Set aside.
In a medium bowl, stir together the shortening, honey, brown sugar, turbinado sugar, oat flour, cinnamon, oats, and salt. Using a fork or your hands, work in the shortening until crumbs form. Be sure to mix this thoroughly so there's no big lumps of shortening. Pile the crumb topping on top of the scone dough. Press it evenly into the disc, reaching the edges, and creating a fairly even layer. This will make your dough disc a bit thinner- about 1 inch thick. Cover the dough disk with plastic wrap, and chill for 30 minutes.
While the dough is chilling, preheat your oven to 425 degrees F, and prepare a second pan with parchment paper. Remove the dough from the fridge, and use a knife or bench scrapper to cut the disc into 8 even triangles. Place onto your parchment lined sheet pan, leaving an inch or two between each scone.
Bake for 14-17 minutes, or until the scones are puffed and golden brown on the edges and top. Let the scones cool on the sheet pan for about 5 minutes, and then use a spatula to move them to a cooling rack. The topping will have bubbled over the sides of the scones- and that’s ok!