This is a bug report for AV Foundation. I noticed this problem when creating nice vector versions of the 1D barcodes used in figures in my book. The problem with this is that if you are scanning Code39 barcodes you have no way to determine whether it was one with or without check digit.
It’s filed as rdar://18566595 and on Open Radar.
Update Oct 17th: Added Apple’s response “behaves as intended” with a very good explanation given.