The warm-up time of the automotive xenons is regulated so that they reach 75% of output in less than 2 seconds (SAE J2009). However, although the current during the warm-up is large (maybe 4x the steady-state current), the power delivered to the bulb is roughly constant since the warm-up voltage is so low.
Since most, if not all, of these flashlight designers use ballasts that were designed for automotive use, they inherit the fast startup times and high initial current draw.