This is expected behavior: this "recurring" designation is necessary to save your customer's payment information for future use without re-entering their CVC code each time. The "recurring" flag does not necessarily indicate the customer is subscribed to a recurring billing plan, only that the card was saved for future charges.
Due to PCI compliance, Stripe cannot store CVC codes on our servers. Payments made with saved payment information are marked as "recurring" to inform card-issuing banks why charge requests are missing that information. This increases the likelihood that the charge will be approved, as it tells the bank that the CVC code isn’t present because the payment information was stored for recurring use.