Combine rolled oats, flour, brown sugar, and cinnamon in a bowl, then drizzle in melted butter and toss until the mixture looks evenly moistened and clumps when pressed. This should hold together like damp sand for firm slicing.

Press the oat crumble mixture firmly into a 9-inch springform pan, smoothing the surface as compact as possible. Chill for 20 minutes to set the base.

Reserve 1/2 cup of the crust mixture for the crumble topping, keeping it separate from the pressed base. Set it aside at cool room temperature while you prepare the filling.

Beat cream cheese, both sugars, vanilla, and cinnamon until completely smooth with no visible lumps. Stop and scrape the bowl so the mixture stays uniform.

Fold in whipped cream until no streaks remain, keeping the mousse-like volume. Mix just until combined so the filling stays airy.

Spread the filling over the chilled crust in an even layer, smoothing the top. Work quickly to avoid softening the base.

Stir cinnamon and nutmeg into the apple pie filling until the spices are evenly dispersed. Spoon the apple mixture over the cheesecake and spread to the edges.

Scatter the reserved crumble over the apple topping to create an even, crunchy layer. Lightly tap it down so it adheres.

Refrigerate the cheesecake for 6 hours or overnight before releasing from the springform. The texture should be fully set and slice cleanly.