Yes...other than assuming driver and full tank of fuel, it makes sense.
The max tow capability would be with an empty truck. Doesn't matter if you load 1 ton of cement blocks in a trailer or the bed of the truck...the engine will struggle just as much climbing the same hill.
If you read the posts on the forum, you will find this is well known and as often as not, the tow rating doesn't come into play. Particularly for 5th wheels it's payload that is the limiting factor and most people just laugh when they see 1/2 ton trucks with 10,000lb tow ratings because under normal circumstances it's near impossible to tow that much and keep the tongue weight high enough not to create a sway issue without exceeding payload capacity.
