Negative because of
1. Security 1. Validation risk: who programmed the wallet? Where is the source code?
2. Security 2. surface of attack. Embedding the wallet directly on the phone greatly improves the surface of attack of potentially malicious attacker.
3. Privacy. Embedding a wallet in a phone link my wallet to my IMEI, that is linked to my identity. That phone comes with an embedded KYC
4. Personal security. Hanging around with such a phone signals you are interested in crypto. So you are exposed to physical attack. Even if you dont actually hold any crypto in the wallet you are exposed to such a risk. (here an always relevant XKCD strip:
https://xkcd.com/538/)
Instead I cannot think of a single advantage of carrying such a phone, instead of a regular phone with an open source app installed (second best, apple with a well known wallet)