Bells started ringing for me before I got to the end of your blog... I thought about it from the other end of the problem where I'd want to append a series of binary files using /b.
Technet articleQuote:
Combining files
If you specify more than one Source, separating entries with a plus sign (+), copy combines the files into a single file. If you use wildcard characters (that is, * or ?) in Source, but you specify a single file name in Destination, copy combines all files matching the file name in Source and creates a single file with the file name specified in Destination. In either case, copy assumes the combined files are ASCII files unless you use /b.
Yeah, I know who you work for and I'm not trying to make you feel any worse here. Hopefully you'll draw a tiny bit of comfort about the fact that this was at least documented behaviour. 
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