I can see the debate over this question, however, I'm going to side with this statement:

"The physical file name of the Resource database are mssqlsystemresource.mdf and mssqlsystemresource.ldf."

It's my opinion that the question's use of the shorthand name, which microsoft also uses in documentation, is ok.

Either way, I enjoy the community's input...gets me thinking in the morning.

source: http://msdn.microsoft.com/en-us/library/ms190940.aspx

Cheers,

Jeff