Before AI, it was impossible to measure productivity. Some tried with misguided metrics like lines of code added but that just incentivized writing obtuse code.

What has changed?

vibes maybe?

If effective AI enhanced SWEs can ship features in a week, the guys who ship 1 feature a quarter stand out more?

Impossible to measure in absolute terms but I think it's clear productivity increases relatively when LLMs are used. At least that's my strong experience.