Coinbase to Coinbase off-chain transaction fees? When I click on "Send" from my bitcoin address which I know is off-chain in Coinbase to another Coinbase address which I also know is off-chain. So technically the transaction will not touch the blockchain, just update their off-chain books locally. 

I know it's off-chain, because I deposited money using my credit card, and I scanned all addresses under Tools > Addresses on a blockchain explorer for a few days and there's nothing in there. They're keeping it off-chain until I actually want to spend it. Granted, but if I spend it to another Coinbase off-chain address, they should be able to find out that this is an address they own and they don't need to utilize the blockchain at all and could do it all off-chain as they own both addresses. 

If that's the case, why is coinbase still charging me network fees? Sounds like mickey mouse fees to me for updating a record in their database without touching the blockchain. 

Are they assuming that I don't know it's a fully off-chain transaction, and think they can charge me regardless? Or does their wizard have a glitch ?
Does Coinbase pay miner or network fees when sending digital currency? is stated clearly here "Any transactions sent between Coinbase customers by email address take place off-chain (not on the blockchain) at no cost".
 Maybe Coinbase have a system that charges network fee as long as "addresses" are used.