I totally agree with this point, but I don't see how the topic we're discussing would be seen that way.
From a "common sense" point of view (which I know, financial regulation is absolutely not), no matter what you call this act of giving someone extra credit (let's call it "interest") for your service based on the amount they've previously paid for your service (let's call it "deposited"), you're still just giving them monopoly money that serves a single purpose and that is to use more of your service.
If they can't turn it into cash, why should any financial authority care? It's got nothing to do with them.
That said, to take your side for a moment, what's to stop me depositing boat loads of cash up front to pay for your service using the "interest" you'll give me, rather than paying it regularly out of company earnings? Now it starts to sound like something a financial authority might take interest in (pun intended).