Going out of one's functional boundary is not so uncommon. Will like to site an example which resulted in not so good outcome.
Different teams provide very useful functional inputs while backlog grooming. But many times they provide inputs close to release, which is fine given it follows the process.
I remember once multiple QA's huddled around me and were trying to arm twist me in changing a UI flow which 'they thought' was right. I didn't negate the suggestion, but requested them to check with Product Owner. To my surprise they wanted the change to happen then and their !!!! . Thankfully I held my position.
But many developers are not like that. In one of my earlier project, something similar happened, where QA reported a UI error message appearing in an unexpected flow. On analysis found that error message was not required at the first place.
Dug further and was surprised by the reason - A recent guideline was given to QAs to ensure unit test code coverage for the functional areas marked as critical. (Not sure how QAs can track unit test coverage ? )
Blindly following that policy they asked for the code coverage for a negative flow, which was not practically possible. And hence an error message was specifically added, to ensure what QA called a proper code coverage !!!! ahem... !!!
Obviously the developer should have stood her ground. But to make things worse even the team architect approved the approach. Result - A wrong UI error message.
Not sure if a single person can be blamed here, but overall teams should always take a firm stance when someone is trying to encroach out of their permissible limits. Not because of pride issues, but to ensure correct meaningful output.
