You are right, it seems like he changed the rule. The only thing that is different when you self-promote as you already said is that you won't get 10SBD. Which is totally normal if you think of it since this money is used to reward people who find good posts.
The title of this post is "Upvotable Day 2: First Results and Self Promotion Now Open!"
Maybe I'm disqualified from the 10SBD reward, but I think we're allowed to self-promote.
You are right, it seems like he changed the rule. The only thing that is different when you self-promote as you already said is that you won't get 10SBD. Which is totally normal if you think of it since this money is used to reward people who find good posts.