I put together this demo patch.
It creates a 6 channel wav file using sfrecord~ and attempts to get info using sfinfo~.
It works fine for aif files but not for wav.
The 6ch wav file plays fine in the quicktime player.
It opens cleanly in Adobe Audition.
If you resave it from Audition sfinfo~ can read it properly.
So there seems to be some incompatibility between the file written by sfrecord~ and reading it with sfinfo~.
Or I could be doing something wrong. Any thoughts?