Yeah - it's a tricky one.
Typing your seed phrase ONCE into a machine that has a keylogger gives your adversary the chance to empty your wallet at any time they like in the future.
You _think_ you've a nice secure Trezor wallet but unfortunately 2 years ago someone keylogged your seed phrase.
When you transfer into your Trezor the winnings of the Xmas 2017 Bitcoin Global Lottery (Congratulations on winning that!) you see all your bitcoins instantly evaporate.
If the seed phrase is only ever shown on the Trezor secure display it's a much tougher nut to crack.
Thanks. I see mytrezor.com never knows the seed order but the Trezor prompts for random order so spyware still has to sort the words and 24 would be hard to sort. I like the idea of a chart of all seed words and associated number and the person enters the seed by using the PIN pad and spyware would not know any of the words.