That works, of course. But there's no particular reason to use Tails, since you're staying offline. Tails is only different from other live os'es when using it online, any live os would work for this purpose.
Isn't Tails' main feature that it is amnesic and doesn't leave any data between sessions (aside from opt-in persistent storage)? Or any other live OS would act in the same way?
This should be obvious, but Electrum which included on Tails isn't up-to-date. Bug regarding wallet/seed creation don't happen and new address/wallet standard rarely changed, but people should know about this fact.
I've installed Tails on a USB one year ago and it had some really ancient version of Electrum, something like 2.7.9. It obviously couldn't open my SegWit wallets so I had to install a newer version brought from another USB drive.
if someone is really paranoid enough to do something like this then they must also be paranoid enough not to trust Electrum itself specifically its random number generator engine. for these people using computers is not a good suggestion.
instead they can use physical ways of creating their private keys using dice, coin flip,... there are also enough articles about how to use these methods too.
Paranoia can be dangerous if it is combined with lack of fundamental knowledge, such people can end up creating their own crypto, generating weak random numbers or just simply encrypting too much and then losing their keys.
For me, what works better is an air-gapped/never touched the internet VM in virtualbox , in which I've installed a downloaded and signature-verified copy of electrum as my cold wallet.
VM's can't be considered air-gapped, if the first layer is pwned, all next layers are pwned too.