I’m no expert on this subject by any stretch of the means

This is a mash up of “by any stretch of the imagination” (as much as anyone could imagine) and “by any means” (by any way possible).  Both phrases involve extremes, and share the words “by any”, hence the confusion.  A salute to Barry Eigen (who by the way is a stretch of the nice)  for hearing this one in a class and sharing it with us.