My attorney seems to think that unless you specifically label the property in the trust as community property you would not qualify for the 100% step up. I'm a novice at this stuff so I can't qualify his position on this one.
I have now spoken to Liberty Mutual, State Farm, Amica and Travelers. All four companies confirmed they can add the trust as an additionally insured. So I think this is looking like an Allstate quirk, or possibly just my agent being incompetent.
Amica surprised me with a quote of only $429.00 for a $5M umbrella policy. Their overall pricing was the lowest of the four as well. And, Amica scored #1 in customer satisfaction from both JD Powers and Consumer Reports, so I'm leaning toward going with them.
But I will speak with each of the brokers next week just to confirm everything before making a decision.