It's just the direction they took with the album. If Jon's vocals were mixed in a dirty way to hide his damaged vocal chords and the instrumental part of the album was to sound cleaner it would sound really disjointed. But, I do believe it's less to do with covering up and more to do with sounding relevant. More and more records these days sound like that. It's not just a Shanks thing, it was a creative decision made by the entire team. Check out Richie's album, a number of tracks are mixed that exact same way, I can barely hear 'Burn the candle down' because of it.

Just wanted to add, people can say all they want about John Shanks, and I might even agree on some points but, The Circle was beautifully produced, mixed and mastered. Definitely light years ahead of WAN....