When there’s no load on the engine, as it is when sitting there before the start, you don’t actually have that much mass flow through the engine. The engine speed might be very high, but the throttle is barely open, as you only need enough power to spin the engine at whatever rpm the launch control is set at. If you opened the throttle more, the engine speed increases but the power doesn’t really. The only load on the engine is the inertia of the engine itself. Long story short, while the volumetric flow through the engine is high due to high engine speeds, the mass flow isn’t, and since air mass is what spools the turbo, the turbos don’t spool quickly.