Jami extensions for Android and Jami extensions for Desktop could be in one file; however, it is often chosen to distribute the extensions separately for Jami for Desktop and Jami for Android to have smaller file sizes.
The Jami extensions for Desktop include multiple architectures (GNU/Linux, macOS, and Windows), and the extension preferences system is designed around a declarative mechanism to allow a native presentation of extension preferences across various Jami applications (i.e., the Jami client and the user interface (UI)).
The JXD (Jami eXtension for Desktop) file extension and the JXA (Jami eXtension for Android) file extension could be merged to the JXU (Jami eXtension Unified) file extension, as the Jami extension system is a unified format.
Unfortunately the "marketing" name for plugins was changed to extensions after years of development, and it would be too much work to change everything to extensions.
Currently, the consensus is to keep the JPL file extension, even if it is inconsistent with the UI, as most users would manage extensions through the Jami UI.