The productivity depends upon the requirements.
If slop is fine (and sometimes it is), the benefits are undeniable. If the dev was the kind that would have produced slop anyway - again, undeniable boost.
If the quality needs to be high I think it actually can slow you down, though.
Agreed, but also to expand, if the dev is mediocre and ai-assisted coding is a skill, the productivity gains are 10x more mediocre code. Since code is a liability, this is not desirable. Hence, mediocre devs being more productive is an underestimated problem of the age of ai-assisted coding. I see this every day.
The result is a whole bunch of dysfunctional systems unnecessarily dislodging perfectly acceptable processes.