Though also when breaking down the study earlier to more experience developers, a similar same pattern of within margin of error change or decrease in productivity shows in that metastudy

They are also not comparing the same metrics here. The earlier study is looking at number of commits and pull requests as a metric for productivity. The other is looking at the time per task

Number of commits / PRs / similar kinds of metrics like lines of aren't great for measuring productivity in general and especially here. Usage patterns with AI could very easily change your commit pattern and PR patterns without changing how much you are getting done