Except that I don't have to be willing to spread my genes, just to undertake actions that will in turn spread my genes. Maybe expense of life is accurate, but surely leisure includes sex and even the pleasures that children can bring.

Right, that could have been more precisely worded, but I opted for brevity with the understanding that people would know what the more precise version is. That would be something like, "...unless you feel desires to put your life and minimization of effort at risk to do things sufficiently similar to those which, in the ancestral environment, increased inclusive genetic fitness."

Even if our desire was solely to spread our genes and not to have sex, this still wouldn't hold true, in that just because you have been constructed by a process of natural selection on creatures that do spread their genes, does not mean that you won't have a mutation that causes you to not feel the need to do so.

Yes, the relationships are probabilistic, both on the reward side, and (I should have mentioned) on the "you"-side. Likewise, Omega can guess incorrectly that you'll one-box, you may be a "never punish anyone!"-type in a society of defection-punishers, etc.