Precisely, IOW they're just for show and are basically GIGO when you're completely honest, but they're a psychological device required both externally (as leverage one way or another towards clients) and internally (it's motivating to see
something go forward, even when you know it's completely bollocks†). Just to say that this definitely subscribes to the basic idea that they "are meant to project an idea of objectivity".
BTW, you forgot the part about giving improving metrics to satisfy management and maybe get a raise (vs 100% not getting one), or a nice story line about how you managed to improve team velocity YOY by 50% through magic on your resume, which in the same way is "reducing an engineer to a few quantities" and equally "turns my stomach" as for alexandercrohde. Most of the things I've done to introduce improvements are immeasurable because they're changes that are mindset shifting or technological leverage therefore there is no metric associated because of the pervasiveness of their effects.
† if you're doing, say, 10 push-ups, instead of "1, 2, 3" try counting each number twice, like "1, 1, 2, 2, 3, 3". Magic, you've done 20. You know it's a mind trick, but it'll still work.
†† Going from email+phone+hallway communication, silo'd knowledge and SPOF Bus Factor to a serious issue tracking, knowledge sharing, and automation on GitLab. Going from manual machine building to fully automated system provisioning and one liner deployment. Any associated metric would be either completely immaterial (e.g confidence and well being) or produce an off-the chart ratio (just computed one just for fun, that's a ~1800% improvement in human cycles — not even counting failure modes — it's so beyond ridiculous it doesn't even mean anything).