Well, it's not a bad idea to put a small amount of coins on your mobile wallet as your pocket money. In my opinion, as long as there is problem there is a solution or there will be a solution created for the problem to be solved. I think having a vast knowledge on how to keep your assets as safe as possible. I think it's what I can only think of about how to keep your crypto assest the safe
However, I still don't agree that we have to separate funds and store part of them in phones. It's too risky, because there is another reason that we might more easily to lose our phones than computers or laptops.
Actually, there is a solution that you won't lose the coins that has been stored in your mobile wallet. In my country, there is a site where it is used to buy/sell btc and it is also a wallet to store your BTC in which that it's what I am using to store my btc I have and they also have a mobile app. This is my solution on getting back the small amount of coins stored in the mobile wallet and let's put it in this situation that your phone is broken, stolen or you lost your phone for example so, that is why creating a back up will help you recover the small amount of coins that's been stored in the mobile wallet. I think that most mobile wallet is a mobile app then, if you have a mobile wallet app then it is best to install an Android Emulator on your computer and then you also have to Install the mobile wallet app in the android emulator you installed on your mobile phone so, even if you have lost your phone you can still access or log in your account you use to log in. Here is a link about
Useful Application that you can use in a computer/PC and there is also a link in the thread about another android emulators that you can use to back up your mobile bitcoin wallet and some android emulators doesn't use much space when installed.