Strange that they don't count comments IMO. My first reaction was that I like the self-promotion rules because the ones I'm familiar with just require posters to interact with the community. i.e. For every post to their Youtube channel/whatever there need to be ~9 comments.
I always liked that because it prevented the subreddits I browsed from becoming giant ad spaces where content creators just dump a link to their video on all related subreddits and move on. If someone is never answering questions asked of them in their own threads and not participating in discussions in any other thread then they're more of a leech on that community than a contributor IMO. I like the idea that in order to have access to the views of the community, you need to also view other people's work within the community and interact.
But to count only posts is weird for sure. I don't feel like the rule really helps anything. For example if I had a channel that was relevant to r/pcgaming to meet the rule criteria I feel like I'd just post my content, then post 9 other inane threads that I didn't really care about/intend to participate in. "What's your opinion on Final Fantasy XIV?" "Someone explain to me why Epic Game Store is so much worse than Steam" "What games are you getting from the Steam Summer Sale?!" etc. etc.