You could, but why? Remember that what you're doing with secure cold storage is buy time: time between when your seed container gets stolen, and funds get cleaned out. The more time this takes, the more time you have to move your funds to safety.

Re: the "old" part, old phones often have hardware/firmware weaknesses that are actively exploited. As of April last year, everything older than an iPhone 12 or Pixel 6 (and apparently every Samsung ever made) is basically instantly(-ish) crackable through hardware/firmware/os exploits, so keep in mind that you may have a lot less time to move your funds out with older phone models; also see #616858

I'd not store the seed on the phone as a production secure device. Maybe for tinkering on testnet it can be fun.