Yes, tapping the baking tray improves the crispiness of the cookies
Sarah Kieffer's technique of intermittently dropping the tray during baking deflates the dough and creates cookies with wavy edges and chewy centers.
The technique of tapping the baking sheet helps the slightly puffed-up cookies spread, giving them a varied texture. The dough deflates, preventing the center from becoming too dense, and the edges flatten into a series of crispy waves, creating an extra chewy cookie center. Freezing the dough is an important step that prevents the cookies from spreading too much, and a baking sheet lined with aluminum foil results in especially crisp cookies.
In Kieffer's recipe, she suggests tapping the baking tray intermittently every few minutes. But she's not the first baker to tap a baking tray on purpose. Before Kieffer's cookies became social media stars, other desserts required a slightly different method for tapping the tray. After filling and before baking, even the most delicate macarons are dropped onto the tray several times to remove any remaining air bubbles in the batter. While the final texture is quite different, both processes allow the baker to help the batter spread without touching it and causing additional marks or dents. Freshly baked cakes should also be dropped for even baking. Next time you need a little excitement in the kitchen, don't hesitate to tap some pots and pans.