Yep, some people do this as a method of cold storage.
unless the phone that was used to create this wallet has never been connected to ANY NETWORK and will never be connected to any network in the future, you can not consider this method a safe "cold storage" method. it would be like buying meat then leaving it outside under the sun for a couple of days and then refrigerate it thinking everything is fine now that you've frozen the meat!
Very strange analogy but I agree with your post.
In my opinion whether that phone is ever going to connect to a Wifi or cellular tower or not, cell phones are NEVER considered cold storage because they can easily transmit data.
Unlike a laptop that you can open up and take out the bluetooth and wifi adapter, you can't do this with a cell phone.
Androids are full of malware and who knows if his seed was leaked in some way. Even deleting the wallet might not remove all traces. The hacker might just wait for a deposit and then sweep all the funds.
My advice is to just get a hardware wallet or use Electrum in cold storage mode. Never a cell phone.