"On the other hand, a services business might not be ideal for a hyperbrain, since clients naturally care about the work you’re doing for them now, rather than the work you did for other clients in the past."
Probably you're right that services aren't good for "hyperbrains", but I don't think that's the cause. In a services business there is something you build, and that's your reputation. As your reputation grows, your prizes grow too, and also you get to be pickier about the kind of work you choose. So that's the backlog of the services business.
So while you're right that a backlog is useful and needed, it can be derived from the services business too.