Streusel: the crumbly cover is not the whole foundation

Useful to know

Streusel is a crumbly topping. King Arthur’s Peach Streusel Pie combines butter, flour, brown sugar, oats and nuts above the fruit filling. [1]

This recipe also has a separate pastry base below the fruit; the streusel does not replace it. Compare the whole cross-section with a fruit crisp rather than only the similar topping. The source describes protecting the surface if it browns too much. Golden crumbs do not prove that the fruit and bottom crust have finished baking.