Not necessarily.

https://www.copyright.gov/engage/musicians/

There are two different kinds of music copyright, and the sheet music only matters for one of them.

Yes, I know that. Which one was Sheeran accused of infringing, though?

No idea. I didn't follow the trial. But one of the things I was originally responding to was "even Sheeran played them as a live medley" which is only relevant in the context of a performance, not a composition.