not true.
favre is not a "mentor". he even said so himself when rodgers was drafted. "i am not here to help him, im here to do my job". he was not explaining coverages to aaron rodgers, nor was he giving him advice on the finer points of dropping back, calling audibles, or anything of that nature. favre is not a practice nut, he skips training camp because he feels he doesnt need it, and hes not a very cerebral player so talking to him wouldnt give you any better an idea of how to play than watching him draw routes in the dirt.
the only "mentoring" favre did was playing the position and allowing aaron to watch him from the sidelines.