That's the same limit for Pay Over Time on all their charge cards including the Centurion. It's a maximum. They use this 35k number when they securitize a bundle of these. They sell these notes to institutions and the 35k is useful as an individual risk limit. It doesn't mean you can run up 35, 1k charges and pay it over time. Approval is still subject to their internal limits which are based on your history.
You're right it's not a great deal. For one thing, like Credit One, interest accrues when the purchase posts and there is no grace period. Still, the interest rate is better than Credit One.
Also, it's best to wait for a good MR offer before adding it. Amex regularly sends these to me with various MR levels from (5k, 3k, 10k) for signing up.
It came with 10k MR points.