You can find a few thoughts about the blue vs purple match-up here, from my opponent and me after a 9-1 series: [MMM1] Game 10: P1 Purple (HolyTispon) vs P2 Blue (Dreamfire) - #17 by Dreamfire
Truth was my go-to tech 2 plan, and IIRC @bansa also went for Truth at least as often as Peace in the series against Frozen. So it’s definitely not just because of Peace. I’d say it’s mostly about purple having trouble applying pressure early, which lets Blue get into its groove - which is very difficult in its matchups against Black, Red and White.