Using BITCOIND RPC require interacting with the Blockchain, and therefor downloading entire Blockchain is required before starting accepting Bitcoin Payments.
Or I am wrong ?
You are wrong and it is clear you didn't read the thread at all. OP can use bitcoin-cli to interact with blockchain.com's RPC interface which they made to be compatible with Bitcoin Core's. Installing bitcoind does not run bitcoind nor does it download the blockchain. He isn't using bitcoind at all. bitcoin-cli doesn't need access to the blockchain either, it's just a dumb client.