Coinbase credit card purchases posting as a cash advance. What you guys think, Why?

Hi I am sure you guys noticed that coinbase recent changes about credit card purchases posting as a cash advance. 

My last 2 purchased were on 26th Jan and 28th jan and I noticed I got charged cash advance fee $5 on both transaction29th and today I got email form coinbase. 

Funny part we didnt get notice about it just got charged . And after a week coinbase sending message out-

Here is the message from coinbase I just got

Dear Coinbase CustomerWe’re writing because you have a credit card on file and want to inform you of a recent change that may increase the cost of purchasing digital currency with a credit card.
Recently, the MCC code for digital currency purchases was changed by a number of the major credit card networks. The new code will allow banks and card issuers to charge additional "cash advance" fees. These fees are not charged or collected by Coinbase. These additional fees will show up as a separate line item on your card statement.
Coinbase does not know whether or not your card issuer collects these fees, nor do we know how much they might collect. As a result, we would strongly suggest switching to a debit card or bank account as your primary payment method. You can do that on the following page: https://www.coinbase.com/settings/linked-accounts.
We apologize for any inconvenience this might cause

BUT

I heard people who used debit card also got charge $5 fee but i dont see anything about debit card in above message.

Anyone else here have any info about it?