Thanks-I'll check out Porterfield's take.
Here's an interesting quote from Peer:
"The records wouldn't have been any good if Jimmie had sung with this group (Tenneva Ramblers)," said Peer. "He was singing nigger blues and they were doing old-time fiddle music. Oil and water don't mix." [Guitar; An American Life by Tim Brooks]
It seems to me that Peer was responsible in part for breaking up the group. He probably said something similar to them at the audition. His interest was only in the Tenneva Ramblers at the time.