I’m not sure that will ever be able to work the the same, though. Because Monzo don’t have advance knowledge of when your subscription will come out, they won’t know when to transfer out of the pot in time.
The easiest way for solving subscriptions would be to debit from the main account first, and then transfer from the pot afterwards to cover the payment. But as this is exactly the opposite of how it currently works, I can understand why Monzo aren’t leaping to this solution. Plenty of customers would surely find it massively confusing.
As such, while workarounds may seem counter-intuitive, I’m afraid they’re probably your best bet for the time being 