Yes, moral propositions have truth-value...
But are those truth-values intersubjectively recognizable?
The average person believes morality to be about imperative terminal goals. You ought to want that which is objectively right and good. But there does exist no terminal goal that is objectively desirable. You can assign infinite utility to any action and thereby outweigh any consequences. What is objectively verifiable is how to maximize the efficiency in reaching a discrete terminal goal.
But there does exist no terminal goal that is objectively (intersubjectively) desirable.
If you mean intersubjectively say it. Objectively has a slightly different meaning. In particular, see 'objectively subjective'.
In You Provably Can't Trust Yourself, Eliezer tried to figured out why his audience didn't understand his meta-ethics sequence even after they had followed him through philosophy of language and quantum physics. Meta-ethics is my specialty, and I can't figure out what Eliezer's meta-ethical position is. And at least at this point, professionals like Robin Hanson and Toby Ord couldn't figure it out, either.
Part of the problem is that because Eliezer has gotten little value from professional philosophy, he writes about morality in a highly idiosyncratic way, using terms that would require reading hundreds of posts to understand. I might understand Eliezer's meta-ethics better if he would just cough up his positions on standard meta-ethical debates like cognitivism, motivation, the sources of normativity, moral epistemology, and so on. Nick Beckstead recently told me he thinks Eliezer's meta-ethical views are similar to those of Michael Smith, but I'm not seeing it.
If you think you can help me (and others) understand Eliezer's meta-ethical theory, please leave a comment!
Update: This comment by Richard Chappell made sense of Eliezer's meta-ethics for me.