I know all they want to allow for a simple clean repair job. They take account anything extra that has to be done. You engines that looks like they been ran thru a mud bog with frozen fasteners that has to drilled and helicoiled. Or mounted in a machine that you got to take half apart to even get to area that needs repairs.
Sorta a Briggs Twin here that needed a sump gasket replaced. Briggs allows 45 min to get it done but it take half a day to get the engine off, repaired, and back on the Super Z. What worst is the new Briggs failed within two passes of the customer's lawn so it was be done all over again. The second time around I use much better quality after market sump gasket. Four months and no problems reported.