The way I look at it, you certainly do not want to set the governed RPM higher than 3,600. Basically, the max RPM governor setting is chosen to protect the engine from "flying apart" and also to keep the valve springs from entering the "float" or flutter stage of operation. Valve springs are only able to return the valve to the seat by their own tension. If you spin the crankshaft fast enough to make the piston "outrun" the valve springs, piston hits valve and then it just gets worse in terms of damage. You know the engine is making its greatest torque at 2,500 RPM, so any additional RPM doesn't make the engine more powerful, but it does allow you to accomplish the work faster. But, that does not mean you can run the engine a 2,500 RPM and do the same work, albeit at a slower rate. The debates of whether to advertise using torque ratings or horsepower ratings leaves a lot of room for clarification. Look at it like this, if you are plowing a garden, or towing a cart of material uphill, torque at XX RPM is important and there is no benefit to be gained by increasing the RPM above the point of "peak torque RPM", except that you will travel faster. But when you are "mowing", you need the RPM to be high enough that the blade tip speed will be great enough to cut efficiently. Setting your RPM to max out at 3,600 will protect the engine and will not affect the engines ability to make power at lower RPM ranges. Or you can set the max RPM at 3,500, or 3,400, or lower, so long as the "mowing mode" still produces the quality of cut you desire at the lower setting.

Top engine speed varies depending on application. 21" rotary mowers are set 3000-3100 rpm because of blade tip speed regulations. Many if not most rider engines are set to run around 3300 rpm, 3600 rpm is usually reserved for generators. They need to run at this speed to produce 60 hz.
This is the main reason horsepower ratings are no longer advertised. The manufacturers were using the figure the engine could produce at 3600, not necessarily what it actually put out.

Thanks a dozen, Fellas (I always felt that "thanks a million" is overkill.) Being a guy who wears suspenders AND a belt, I'm gonna shoot for 3500 ... if my neighbor will lend me his laser tach again. Sincerely, I do appreciate it.