On Agile teams, traditional job boundaries start to blur. Testers are more involved during development. Developers write tests. Testers and developers help with documentation. Team members pitch in to do what needs to be done. And in this process, they broaden there skills. People don’t lose specializations, but they become more generalists.
This is a good thing.
Static functional job boundaries have (at least) three downsides:
Cross-functional teams, OTOH, can adapt more quickly, see the system more broadly, and learn across functional boundaries.