Or you can look at it the other way. Total GCM is
If you tow 3500 kg, you can only carry 300kg in the car.Similar with Colorado.
If you need the 3.5 ton towing, you can do it, but with limitations.
I actually prefer Toyotas method. It's 2500, regardless of vehicle payload. No confusion or Gray areas, and to be honest, it a more realistic figure. 3.5 ton being towed by a basically unloaded ute is not ideal.
I'm critical of Toyota when it comes to the Prado 2500 tow rating. I see it as ensuring 200series sales. But on hilux I think they have it right.