Nice strategy.
Another path: This won’t show you what the callbacks actually return/process, but you might take a look at the callback graph for your app in debug mode. It’ll also show you the runtime for each callback.
If you’re looking for more detailed traceback of the performance of callbacks etc. you should also check out this post about Werkzeug profiling: Performance Profiling Dash apps with Werkzeug - #2 by chriddyp
It’s plausible to me that you’ve already done this, but should at least be helpful as a parallel path to monitor when callbacks run in your app.