Even if they are a voice acting-tier backer, so what?
Voice actors are usually placed under non-disclosure agreements that are every bit as strict as the ones everyone else are under. I'd be surprised if they were allowed to share details of the character they're voicing, let alone the crap this guy is claiming.
Furthermore, the voice acting backers are likely going to see some unseen content (namely, the character they're voicing), but I highly doubt they'd get to see the game to the extent this guy is claiming. The tier was "voice a character", not "get a special viewing of the game including unannounced levels and new spoilerific story details, and you're free to blab about what you saw to everyone even though you're not the press".
The whole situation just seems extremely suspect and unrealistic.