In Android, you can check the wallet's type by tapping: "<Wallet name> -> Wallet details".
You should see a "Watch only" tag with an 'eye icon' above the screen below 'Wallet details'.
If he open electrum, he will see the eye icon at the superiolateral side.
He already saw the main screen and still thought that it's not watch only.
Reading the literal "
watch only" text should get him at ease that it's actual watching-only.