OK. I made a couple test files that had a few random pitched and unpitched instruments from each of the S7S, SE6 and VDL templates. Sibelius 7.1.2 loaded the correct pitched patches into the correct devices. However, it did not choose the correct device to even have a chance to load the unpitched patches into.
Since this seems to me to be a new (or broken) software behavior, I rolled my Sib install back to 7.1.0. Thankfully, everything was loaded as I expected it should, and did so in both of my test files.
So, I'll be getting some information together for the Sibelius team to show them what's going on. I'll post again when I know something new.