Maybe a bit paranoid, but not too much.
That's what I aim for. 
If someone should decide to use an Android phone wether old or new make for cold storage then it's expected that the person should have a secure hidden place place that by chance still wouldn't come to the thought of a burglar that anything of value like a phone could be placed there not to talk of a phone used as cold storage.
If you are planning to physically hide your wallet as a main part of your security set up, then a phone is bulky and difficulty to hide. Compare to some of the much smaller hardware wallets which are on the market, or to just a simple sheet of paper with a seed phrase written down. Not only are both a good airgapped hardware wallet or a properly set up paper back up easier to hide than a phone, they are also more "cold" than a phone could ever be.