I think Apple may still be acting with privacy in mind, as opposed to being controlling. Extensions do pose a risk to users when they become popular enough, and

I think Apple may still be acting with privacy in mind, as opposed to being controlling. Extensions do pose a risk to users when they become popular enough, and there have been examples in Chrome where an ad company buys an extension and embeds tracking into it, or otherwise encourages the author to embed ads. It doesn't invalidate the other motivation for wanting extensions to be published in the app store, of course, but I think the privacy use-case is sound.