Previously, to get the product id, the getSku() method was used, which returned singular value.
In the 4.0.0 version of the BillingClient library, the getSkus() method was added (https://developer.android.com/google/play/billing/release-notes#4-0)
In version 5.0.0, the getSku() method was removed totally, and getSkus() was replaced with getProducts(), whose documentation says just “Returns the product Ids.” (https://developer.android.google.cn/reference/com/android/billingclient/api/Purchase?hl=zh-cn#getProducts())
I cant google any information, why product can have multiple identifiers now?