Just thinking loudly here, I guess Co-Author in commits is a hint. PRs where LLMs have been involved is probably another measurement. Github Copoilot has its own account too.

They require disclosure of what tool was used if submitting AI-helped code.

(Which probably means this is slightly underreported from people not disclosing.)

Yeah, I wonder which part of this figure is people doing "let me ask the LLM to do X... aw shucks, that's not how you do X you dumb clanker, fine, I'll do it myself" and not deleting the metadata left by the LLM in the initial draft (a very common scenario in my personal experience). Or people using LLMs for "dumb" large scale changes instead of conjuring an ad-hoc grep+sed script.