I'm pro-Tram here, but suggesting that Tram hasn't given much thought to the implications of his enemy's most overwhelming strategic advantage is not helping his case!
I posted a Tramennis rant on the other board. Here it is.viewtopic.php?f=12&t=1910#p43987
Basically, Tramennis doesn't spend time thinking about military tactics except to give them a good once-over and make sure they're basically sound. Canny, but not paradigm-busting like Parson. While Decryption is hugely tactically important, Tramennis sees the situation as having effectively neutralized it. Even if he considered Jack's plan of reanimating falling mounts and using live mounts as damage sponges to weaken Jetstone's assault, he would surely have concluded, as Jack did, that the assault would still pulverize GK almost to oblivion - and, more importantly to Tramennis, still fail at achieving his primary diplomatic objective.
"But they are still a terribly powerful side. Gobwin Knob could still eventually crush the Coalition, even without the ability to Decrypt our fallen. We could bargain with them in earnest, father."
Tramennis sees GK as locked in the airspace and doesn't consider it further, because nothing in all of his experience in all of the world has given him any reason to do so. If we assume Parson, the Perfect Warlord, is pulling off tricks left and right that nobody in Erfworld had ever so much as considered before - not a bad assumption - then Tramennis really would have no basis of comparison for him. Tramennis has (almost certainly) never, in his entire life, seen such an audacious and out-of-the-box tactic employed, because nobody he's ever encountered has had the right sort of mind to come up with anything like it before. So how could he anticipate and counter it properly?
The situation is rather like a man, cornered in an alley by a bunch of other, more violent men, his every avenue of escape or retribution denied to him...and suddenly he hurls a rope into the sky and climbs up it to safety, suspended on nothing. The mob menacing him isn't stupid for not having thought of him pulling that, they never had any reason to believe such a thing was even possible.