I can understand Hotline telling dealers to turn people away from this. This doesn't seem like a proper fix. Seems more like a short term fix to keep some people happy. The synchros operate off of friction. Hell, one of the guys on one of the forums has already reported shifting problems in all gears now. I think the result lies in a different specification lubricant. As a warning, if you for some reason want to try a different gear lube, GL-5 can damage your transmission do to the large concentration of EP addatives (sulfer). Gear Lube specification (GL-4) is OK for manual transmissions.
2012 Ingot Silver Mustang - 3.7L V6, Performance Package (traded)
2012 HP White Mustang GT - 5.0L, Premium, 3.73 rear end