- Phone gets lost/damaged
Depending on whether you carry the phone with you or just leave it at home in a drawer, this is more or less likely. - Phone gets stolen
If the thief does not know what the seed means, this is the same as a lost phone. However, a thief who recognizes the data as a cryptowallet seed will probably find out pretty quickly how it can be used to access your wallet.
So what's the advantage of storing a seed in such a phone? Do you really need to carry it with you (for example, to enter it into a wallet on a desktop/laptop where it is not normally stored)?
You need a backup of the seed to protect against loss of the phone, and you need to store the seed on the phone in a way that is not recognizable as a wallet seed to protect against knowledgeable thieves.
Overall, looks like a lot of effort for dubious value.
Onkel Paul