On my iPhone (iOS 13) when, in a Secure Note, I click on "attach file", the app opens up to Photos. After I select a photo to include in this Note, what ends up being attached is something called "adjustments.plist", not a photo.
However, on Mac OSX attaching a photo does, indeed, attach a photo.
I'm guessing this is just a bug of sorts....
1Password Version: 7.3.3
Extension Version: Not Provided
OS Version: iOS 13
Sync Type: iCloud