FWIW, using change note durations worked correctly for me. The whole notes became half notes with a stem.

Try this on the Finale default file, add some random notes and run the note duration command. See if it works in this case.

It works correctly for me, as well. You might also look at JW Meter and Rhythm.

Thanks, guys. Pretty sure it's caused by a bug because it's from an xml source file that got opened in Finale. I import a lot of xml and the resulting files end up with lots of weirdness. 

Let me guess: You are importing XML from a scanning program that purports to automatically turn scans into XML. They don't work reliably. You need a full featured program, such as SmartScore 64, that lets you edit the scan before converting to XML. This step insures almost perfect results, once you have learned the program.

I speak with the experience of hundreds of scores.

You might try exporting your XML, and re-importing it. that may help some.

I use SmartScore 64. I find the editing in SmartScore 64 to be very clumsy. And if I could edit things like halfing note values, I wouldn't need Finale at all. I could just do all the editing from within SmartScore. There are actually quite a lot of problems with scores imported from XML that already have formatting in the original version.