I think that report is in error because every camp report has Sherrod at LT in the second group and nothing has been remarked about the position switch. Honestly though, there hasn't been much reporting on the exact nature of the 1st and 2nd lines so far because everyone is fixated on Tretter and Lang's injury.
McCarthy did he as going to work at Left Tackle during the offseason. Usually if something goes against Hoyle, you see some mentions of it.