[zo1]

Sorry, did plenty of "distributed" tracing back in the day and this is just not the case. I can't help but feel like you're after-the-fact rationalizing as if you need this for diagnosing anything "distributed" or "complicated".

Distributed anything is actually easier in most cases because you will always have input and output. Sure, if you're debugging a complicated and coordinated "dance" between two concurrent threads/processes then yeah fully agreed, but then you're deep in uncharted territory and you need all the help you can get.