It is all about phrasing. If you ask it like "I thought this was a X position, doing Y isn't something I expected to be related. I can do it, but I was hoping

It is all about phrasing. If you ask it like "I thought this was a X position, doing Y isn't something I expected to be related. I can do it, but I was hoping you could clarify if the expectation was the ability to do X, Y, or both?" you will likely have a far better outcome than if you come off as challenging them.