Google changed their terminal level to L4, which is a level where you can be do designs with guidance, and implement big chunks of projects on your own. The previous terminal level was L5 ("senior"), where you're expected to own multi-quarter long projects and be a tech-lead of ~5-10 people. Oddly it does end up being structured as a pyramid - lots of L3/L4 folks than L5 folks.
This used to be accurate, but is out of whack now that the big players have scaled back junior hiring so hard. My team (like many others around me) is all L5/L6, everyone writes code and there is less opportunity to lead/direct others since everyone is quite independent.
Even a few years ago, many L5s were more like rock-solid ICs than what I would consider “tech leads”. And an L5 tech-leading 7-10 people I would consider to be an L6 who just hasn’t gotten promoted yet.
You're right that the roles are somewhat flexible: somewhere between raw technical output and technical/design leadership and "program/project management".
