Entitlement isActive is false after opting out of renewal, while it should be true

One of our customers opted out of automatic renewal. She subscribed previously to a yearly subscription, and after a couple of days opted out of renewal. This means her entitlement to that yearly subscription should still be active, just the `willRenew` property of the entitlement should be false. However, the `isActive` property of the entitlement was false.

Only after asking her to restore her purchases, the entitlement was isAcgive again.

Code for checking if subscribed:

Purchases.shared.getCustomerInfo { (customerInfo, error) in
    if let customerInfo = customerInfo {
        if let entitlement = customerInfo.entitlements[PurchasesManager.entitlementPremium] {
            if (!entitlement.isActive) {
                // Not subscribed, but was subscribed?
                if (premium.premiumFromAppStore) {
                    // Logic for ubsubscribing user and informing they're unsubscribed
                }
            }
        }
    }
}

Code for restoring purchases:

func restorePurchase() {
    self.showLoaderPurchase = true
    PurchasesManager.shared.restorePurchases { customerInfo, error, configured  in
        self.showLoaderPurchase = false
        if (configured) {
            if let error = error {
                self.showToast("Error occured during restoring: \(error)")
            } else {
                let hasPremium = customerInfo?.entitlements[PurchasesManager.entitlementPremium]?.isActive ?? false
                self.premium?.premiumFromAppStore = hasPremium
                self.showToast(hasPremium ? "Congratulations. Successfully restored your Premium subscription" : "There are no Premium subscriptions to restore for your account")
            }
        } else {
            self.showToast("Environment is not set up correctly. Please contact support")
        }
    }
}

Is this a bug with RevenueCat or App Store, or am I maybe missing something obvious here?