I thought I would see if I could prove you wrong....
so i just checked to see if i had a save of my GH war (luckily i did), and guess what...
they had one single transport left

, right outside one of my ports IN NORTHERN EUROPE

, where I had a navy stationed

!!!
...so I destroyed it, then tested the peace offers....THEY ACCEPTED my 100% demand immediately (first time)
ive since played on, but that really annoys me, in future if the AI refuses my peace offers (when I have 100%) Im loading up as them to see if they have any troops or ships left, then I shall hunt them down and destroy them!!! Or if they are just minor...delete them, as it is absurd that a country should not agree to my demands because they have one transport or one soldier lurking somewhere... ABSURD!!!!
edit - well its not all that bad

, its only a game, but c'mon, all his lands are lost, his armies destroyed, but the captured khanate holds out for one ship or one man, is one man going to come back and regain all his Lords lands? i guess if that man was Rambo and this was some corny movie...but its not.