This isn't about rudeness or courtesy unless they are responsible for that code,...

mytailorisrich on Jan 12, 2020 | parent | context | favorite | on: Goodbye, Clean Code

This isn't about rudeness or courtesy unless they are responsible for that code, in which case they should be involved or leading the change.

As you mention it's about technical knowledge: They know exactly why the code is the way it is so consulting them is "due diligence".