I get your point about when you use the rear wheel lock and why. Another way to look at the function is that it guarantees 3 of the 4 wheels are pulling while a normal 4WD without the rear wheels locked (differential defeated) only guarantees 2 of the 4 wheels are pulling. I do wonder though -- unless you are experiencing wheel spin while operating (are you?) then I don't see how the wheel lock does anything for you.Tillage and grading. With the 4 wheels clawing through the traction is uneven at times. The diff lock balances this out.
It also helps significantly with an angled blade grading where the machine is getting shoved sideways.
View attachment 5497651