I didn’t try the seed option. I tried only the seedless way.
I think my device actually was online when I setup that. For sure I didn’t remember any advice of getting in airplane mode.
Having said that, this wouldn’t be much more added security, if Tangem were a malicious organisation, nothing would prevent them to make the app (which is open source and audited, btw) to transmit the seed at a later stage.
seedless stuff is really cool, it really inspires me, but after so many years of using seed maybe I'm not ready to use seedless stuff yet
elysium made a very nice experiment to have a sort of fixed data, like pylons, that if always used in the same order give you an equal seed
example if you put
email, your password, your date of birth and more get a seed
but the nice thing is that you don't have to remember the seed but only the data you wanted to use