What is the new "Resubscribe" feature found in Billing Library 2.0 and how is it different than the old Billing Library 1.2.2's?

In the Android Developer Console, I saw this message

Resubscribe isn't currently available for your users because your app does not use Billing Library 2.0 in all active APKs

But, I was puzzled. Currently, we are using Billing Library 1.2.2.

This is how we decide, whether to show subscription button to user or not.

• During queryPurchases, We will perform List<Purchase> purchases = PurchasesResult.getPurchasesList(). If the subscription's SKU is not found in purchases, we will show the subscription button. If not, we will hide the subscription button.
• If this is a new subscriber, there will be no SKU in his purchases. Hence, he will see the subscription button, and allowed to subscribe again.
• If this is a previous subscribed, and already cancelled user, we assume there will be no SKU in his purchases too!!! Hence, he will see the subscription button, and allowed to subscribe to the same sku again.

As you can see, even with old Billing Library 1.2.2, we are still allow user to resubscribe to same SKU again, to his previous cancelled subscription.

If that is so, why there is a special feature called "Resubscribe" (https://developer.android.com/google/play/billing/subs#resubscribe) in Billing Library 2.0? How does it different from our current Billing Library 1.2.2 flow?

from What is the new "Resubscribe" feature found in Billing Library 2.0 and how is it different than the old Billing Library 1.2.2's?