“We’ve just sent a verification code to the email you provided, please type the 4 digit code here:_ _ _ _”
It could even be 2 digits (the same 2 digits for everyone), you’re just looking to get their eyes on the email letting them know additional paid subscriptions are available on your website.
Let's assume you purposefully crafted the email or app to break the code autofill built into iOS.
I think you'd end up confusing users. Most people will go to their email expecting to see a verification code in big bold type. If you make the code less obvious, they'll get frustrated ("I came here to get a code, why am I now doing something else?") It's awful UX at a particularly business-critical moment.
And this is all assuming Apple doesn't see through your ploy and just reject the app.
It could even be 2 digits (the same 2 digits for everyone), you’re just looking to get their eyes on the email letting them know additional paid subscriptions are available on your website.