There are a few facts:
Official add-ons are more trusted than 3rd party add-ons
Normally Official add-ons are alive whenever Xenforo itself is alive.
Official add-ons are updated as far as Xenforo is updated.
Official add-ons are 100% supported and all their features are 100% integrated...
XenForo 1.x ships with many built-in importers and they are present in every install of the software. However, this component of the software is never utilized for fresh installs and it is used only once for those who migrate from an exiting forum software, from there it just sits idle. That...
If Resource Manager could have independent multiple instances, 3rd party addons could extend only a specific instance.
For example in a single installation of xenforo we could have:
an addon that extend an instance of RM to a Shop
an addon that extend an instance of RM to a Classified System...