This is wrong statement. In India, RBI only have the right to issue or recognize the currency/PNote/legal tender etc.RBI is constituted under special act 1934 (which was happened before Independence), even PM can’t interfere the RBI activities. Such a provision had given under this act1934.Few amendments has happened in the act but till date PM or any constitutional body can’t intervene the RBI activities (may recommend but cant order).
Flipkart Vocuker and Amazon credits are not issued by flipkart or Amazon; these are issued by gift card companies(Flipkart- quicksilver, Amazon-GigtBig) and both are licensed under semi-closed prepaid payment instruments by Reserve Bank of India under section 7 of the Payment and Settlement Systems Act, 2007 and mobile recharge comes under closed prepaid instruments( Reference https://www.rbi.org.in/scripts/NotificationUser.aspx?Id=8993&Mode=0).Some time ago sodexo pass also stopped by RBI warning but later they approached to RBI and get it cleared to issue as a meal pass.
Hence RBI only have the right to consider Bitcoin as a legal tender/currency ; only a matter of time until other central banks considers.