The wording is confusing: I would have expected going by the way the mastery lock screen is worded that any free account that purchased EoD (given we're given certain things in advance, ie extra character slots, better access to the trading post, etc) would also unlock core masteries which allegedly require any expansion. It's really not like your example at all: any expansion is supposed to unlock certain things, and it's almost certainly an oversight that everything else is unlocked regardless of what expansion you buy, except if you pre-purchase EoD the one thing that is locked is Core Masteries.