Comment by thephyber
I'm under the impression this is wrong. A trace is made from one or more spans. So long as the context is propagated[1] from one service to another, any number of spans referring to the same trace can be generated anywhere at any time. The trace+spans don't have to be created in the order of a stack.
[1] https://opentelemetry.io/docs/concepts/context-propagation/
This is correct. Traces are made up of spans that can be created within the same process, different processes, different machines, etc. and all emitted asynchronously.