I think the thought process is that game shape correlates with,stamina level and play time for instance i got a 32 yrs old SG with stamina 8,every time i play him 65-75 min he struggles GS hes varying between high end of respectable and lower-mid strong,while i play him above 75 min 80+ hes a proficient,i judge of whether is lower or higher end of form by DMI,seem like the maintaining of gameshape s not black and white after all,and the golden rule seems not to apply on all stamina levels.