I'd pass on the tight connection. The connection flights tend to arrive at the A and B gates. You never know where an ANC flight will depart from. It could be an adjacent B gate or wind up in S. With an arrival at B, a wait for a pink tag bag and a departure from S, you'd be cutting it really close. Honestly, a 30 minute MCT at SEA is too brief. It should be 40 or 45.