I meant the actual React code: handling the click event, running the component code, resolving dependencies and running hooks, building the virtual dom then handing off to react-dom for reconciliation, scheduling updates, and finally modifying the DOM. Not your application code.
The async comment was to point out that if you attach a breakpoint to your `onclick` handler, you will reach 'the end' of execution after less than a hundred function calls. But the actual work (see above) inside react and react-dom hasn't even started, as it's pushed to a queue. This may give the impression that far less code is running than actually is.
This is still in context of "you can read through the library's codebase and understand what it's doing fairly easily"; so yes, it's specific to React being very complex vs something like htmx, which most devs could understand in its entirety in one afternoon.