Yeah, I think their threat model right now is that Qubes locks down your computing environment so well that it is extremely difficult for an attacker to identify you, so the threat of a physical attack is secondary. Of course, an attacker might identify you in many ways not related to exploiting your OS, so they plan on physical defenses in the future. OTOH, Tails assumes there is a high probability you will be physically attacked and your best defense is to leave no trace of your activities. (That is a reasonable assumption for its original user base, political dissidents at internet cafes in repressive regimes.) We all want both defenses: the strongest isolation to protect against exploits and identification, and the best security against physical attacks, but no preconfigured solution offers that right now. Qubes looks the most promising going forward, since they mention defenses against physical attacks in their future milestones, while it doesn't look like Tails has any plans to add VM isolation.