Where are you getting that from? It’s desirable that the user’s name renders on a single line. What matters is that I can change the name template and see the display name updated to reflect that. (The template calls the section “lineByLineFormat”, but that’s just because it shares an implementation with the address template we actually remove the lines from the string).
It will end up being the property getter for the PersonResource here that defines the display property.
You might note, in that function this comment, which implies that the PatientResource does something different, but checking the code there reveals that it doesn’t. (Oddly, the code seems to be exactly the same as it was when that comment was added).
Ultimately, the PersonResource calls Person#getName()#getFullName(). In 2017, getFullName() was changed to use the name template, so I don’t think there’s any work to be done here except to remove that comment mentioned above that may imply that there is.