The loophole being taken advantage of here is that JetPack is basically an agglomeration of 45 separate plugins. If you install it for one of the features, then effectively you now also have 44 other inactive plugins installed.

JetPack is using that fact as the way to get its features top in the search result. It’s a very subtle technical distinction. AFAICT, it’s within the precise letter of the guidelines. But on my understanding, the plugin directory team have always – quite rightly – looked to apply the general principles behind the exact letter, understanding that the letter of the law is not necessarily perfect and may need modifying, or applying on a case-by-case basis.

In my view, here the principle should mean that JetPack shouldn’t be allowed to do this. Just because it’s structured as a mega-bundle of 45-plugins-in-one shouldn’t mean that it gets special privileges over another plugin author who instead structured his 45 features into 45 separate plugins.