I'm not completely sure how the implementation for Blockchain.info works as I have not tried it myself, but from my understanding what you want is to use a single private key with a corresponding public key that allows you to generate new addresses for every payment you receive, without the need to store more than one private key.
This can be achieved using HD wallets which was introduced with BIP32 that the link you have included refers to.
In simple words this features allows you to take a private key and apply a mathematical function to the private key to generate a new private key (with a corresponding public key and address). This allows you to use the first private key to spend all transactions received to address of the public key of the newly generated private key.
This function can also be applied to extended public keys, and therefore generate a new public key that can be spent using the private key of the public key that the newly generated public key was generated from. This means that you never have to expose the private key to generate new addresses, that it can be used to spend received transactions for.
This might be what Blockchain.info does, which in reality means that they do not forward the payment from the newly generated address. This means that you can receive payments to multiple addresses, without needing to spend fees to use one single private key to spend them.
You can read more about this under the section HD Wallets in chapter 4 in Mastering Bitcoin by Andreas Antonopoulos, or under the section HD Wallet (BIP 32) in the book Programming The Blockchain in C#, which are both open source and can be found free online.