That is not exactly what they are saying. Many of the smaller tractors lack position control.. let me attempt to explain.
First lets explain position control: This setup allows you to move the control lever in an arc and stop at any of the numbered positions within this arc. The 3pt moves and stays at a position that corresponds to one of these numbered positions. For example if you put the position control lever to a 4 that is a certain 3pt height. Then say you raise it all the way up then put it back to a 4 it will go to the exact same position. There is a feedback mechanism that keeps the 3pt at this fixed position even as the hydraulic cylinder bleeds down under load over a period of time. The feedback mechanism will open the valve a bit and allow more fluid to come in and keep that preset height.
Now on to the cheaper less complicated 3pt valve arrangements.
These controls have a simple UP or DOWN valve control, with an spring return to center. YOU are the "feedback mechanism" It is up to you to stop the movement of the 3pt as it comes up or goes down by quickly moving the control back to center when the height is where you want it. Also as the cylinder bleeds down this type of 3pt control will just continue to sink the 3pt and YOU are again the "feedback mechanism" that must occasionally re adjust the height as you notice the implement lower than it was 20 minutes ago.
It is not that you cannot put the 3pt anywhere you want it, because you can. It is a matter of will it stay there? It will not over a period of time, it will require periodic occasional adjustment. And more to the point when you need to raise the implement you cannot just put it back to where it was by just lowering the implement to a numbered preset position, you must look at the implement height, and "fiddle" with the UP/DOWN valve to get it just where you want it.
Not to say this is a major pain in the butt. It depends. Some peoples usage does not require this precision control of the 3pt. Let me give you an example: If you have a 3pt finish mower with Wheels on it, you probably just raise the mower fully for transport and lower if fully for mowing. In this case this type of control is of no consequence.
Now lets say you are using a rear blade or box blade and you want a precise height of the 3pt on each pass? Then this will require more work on your part to get it where you want it and keep it there.
There is a variation on this type of standard control valve called 1/4 inching that has a intermediate position of the valve from neutral to UP that will move the hitch in approximately 1/4 inch increments.
So there you have it, the best I can explain it. It is all about convenience and precision control of the 3pt. Of course there is more, there always is, and we can get into the next step up of position control, with mixed draft/position control. .
