Marketplace install does not contain the SDKs

When Installing the Plugin from the Marketplace by Drag&Drop or by selecting it in the UI, only the gwt-plugin itself is shown and installable. The SDK can't be selected and will not be installed.
Using the same Update site from "Install new Software..." will show the SDKs, and they can be selected to be installed. Seems like any Feature must be specified in the Marketplace entry?

Reproduce the installation through the Marketplace drag-and-drop or UI and compare it with the same update site opened through "Install new Software...". Inspect the Marketplace entry and feature definitions; done means the SDKs are visible, selectable, and installed through the Marketplace flow.

索引モデルが issue の本文から書いたものです。