L4 to L5 is no cakewalk. you have to be rock solid in the core SWE disciplines and have excellent communication, organization skills, and very good leadership skills too. looking at the stats, promoted as a % of total for L4 to L5 just makes it into the double digits and only a little over a quarter of all SWEs are L5.

the SWE ladder requires/expects for an L3 to get to L4 by makes no such requirement to ever get to L5.