Yeah, a lot of cross-cutting concerns fall into this pattern: logging, authorization, metrics, audit trails, feature-flags, configuration distribution, etc

The only way I can see to avoid this is to have all those cross-cutting concerns handled in the N1 root service before they go into N2/N3, but it requires having N1 handle some things by itself (eg: you can do authorization early), or it requires a lot of additional context to be passed down (eg: passing flags/configuration downstream), or it massively overcomplicates others (eg: having logging be part of N1 forces N2/N3 to respond synchronously).

So yeah, I'm not a fan of the constraint from TFA. It being a DAG is enough.