... If you write down the seed, someone could view the seed while you are writing it down, or while you are importing the seed into an air-gapped computer/phone, or while you are transporting the paper wallet from your secure location to the location of your computer.
The chances of the above happening may be low, however, they are non-zero, and are in addition to the scope of vulnerabilities of having a wallet stored on an air-gapped computer/phone.
I think we all understand what you are saying, but this boils down to physical security already. If you do everything in a separate room, or one you properly prepared (or you can do what Snowden does and hides under a dark blanket), fire up some white noise or turn up the TV volume to mask ...
"So, there is a chance?" = that depends on how you do it.
For most people, they should not worry about it too much. For people like me who hold other people's coins in escrow, I've grown a habit of doing most of the things I mentioned above and then some; it doesn't hurt that I have other forms of physical security as well, armed guards at the gates, etc. If some government were to specifically target you, then you are screwed no matter what.
Everyone else, 0.000001% or 1 in ^256 = for all intents and purposes is impossible. (Peppa Pig says whistling is impossible! Just put your lips together and blow? It's impossible!)
