It is certainly interesting how it is phrased, but not anything new. MMO companies have been doing that for years now and for Cryptic is is business as usual. All the new issues (content updates) in City of Heroes/Villains were for a long time labeled as "free expansions".

Since it is not well defined what is actually included in the subscription fee, the message will be adjusted to whatever fits the situation.

In this case it is "free" because the marketing wants to point to particular items. Another situation could be arguing about haveing a subscription fee at all and in that case it would be pointed out how much is "included" in that fee.