Pie crust question for custard pies?

If you bake the crust separately, then how does the custard bake? Made custard and coconut custard pies all my life, for business and family....the custard is always baked in the crust. In my 40 years of baking, I have never seen a recipe where it is baked separately and poured into a cooked crust....just doesn't make sense. Maybe the poured recipe is using a Jello custard type product?