The ramp-up time with AI is absolutely lower than trying to ramp up without AI.

My comment is specifically in contrast to working in a codebase where I'm at "max AI productivity". In a new codebase, it just takes a bit of time to work out kinks and figure out tendencies of the LLMs in those codebases. It's not that I'm slower than I'd be without AI, I'm just not at my "usual" AI-driven productivity levels.