Question

In both biscuit recipes, why does the author begin the instructions with "Preheat oven to 450 degrees”?

so the biscuits can start warming before the dough is ready
so the oven is warm when the dough is ready to bake
so the reader can begin warming the butter before adding it
so the reader can keep the various ingredients warm

Answer 1

so the oven is warm when the dough is ready to bake

Preheating ensures the oven is at the correct temperature when you put the biscuits in so they bake and rise properly, giving the right texture and browning.