I thought Phase 4 and Early Access were synonymous as well.
To be clear, Early Access is a preorder bonus wherein you get a code for early access to the actual launch of the game. This will presumably be after the end of Phase 4. It wouldn't make sense to offer early access as a preorder bonus when the game is already available to everyone via the open beta.
Once you preorder, you get an early access code that lets you into the launch version of the game a week (?) earlier than people who didn't preorder.
Edited, Jun 26th 2013 10:21am by Aasher