The Chart you show, just shows 140, and doesn't separate the Crossflows from the Loopers, except by yr, and there is Difference in how much Timing is allowed
In 1985, a completely different Motor became the 140, it was a larger Loop Charged Design. 85 was also the first yr OMC started to Prop Rate their Engines.
As for all the Variances in Max Advance, in the 70s and into the 80s, OMC appeared to be changing the Cylinder Heads and thus the Compression on a lot of Motors, every Model Yr. Lower Compression Heads tolerated more Timing Advance. Shape of the Combustion Chamber also affected how fast the Fuel Burned too. WOT Fuel Calibration also factored in, as a Richer Mixture provided some Cooling, and more timing could be used. Changes to the Exhaust Tuning, also affected how much Air and Fuel were in the Cylinder to be compressed. As the 70s and 80s progressed, Gasoline Formulations also changed, that too affect the Max Timing.
However, I know the 1973 135 had Cylinder Heads that were offered the Highest Compression on the V4s, yet had less Timing Advance than the 75-76, which had slightly less compression
Unless you are the original Owner of a Motor, and know its History, a used Engine could be a bunch of cobbled up Parts, even the cover of the Airbox, where the Sticker stating the Max Advance, could possibly not be the One that belongs to that Motor...