Difference between instant cocoa and drinking chocolate
They are technically different... but it seems that the producers do not always follow the correct terminology in an attempt to sound fancy.

Instant Cocoa is made with cocoa powder, as you stated in your question. It's made from leftovers from the chocolate making process and contains little cocoa butter. Hot beverages made with it are called "Hot Cocoa".

Drinking Chocolate is actually made with actual chocolate, either in disks, pellets or shavings. This means it contains lots of the rich, buttery cocoa butter. Adding it to hot milk causes the chocolate to melt and turn into the delicious beverage "Hot Chocolate".

The terms above are as found on several sites, including the one below... That being said, the "Drinking Chocolate" pictured above, Divine Drinking Chocolate, is not actually drinking chocolate.  It is a sweetened cocoa powder mixture. Divine Site

So, when you're looking for a true drinking chocolate be sure to read the ingredients label.

More in-depth info on the source link.

Source: The Nibble