I accidentally stumbled across this, and I can't find it documented anywhere (nor can I remember having encountered it in the last 2 years) - if a CMSPlugin subclass has an attribute called render_template, the value of that takes precedence over the one declared on the CMSPluginBase subclass attached to the plugin_pool when rendering plugins
I think this is documented on the custom plugins page
In "The Simplest Plugin" page, render_template is mentioned as one of three required attributes on the class. It's also got a title in the "Plugin Attribute Reference" section.
So does that mean this ticket can be closed?
yes this can be closed
I don't see any indication that the documentation adequately covers the scenario this ticket covers; both documentation points cover the render_template attribute on the admin subclasses, rather than the CMSPlugin subclasses.
Looking at the source, the original line linked is still in place, so I expect the issue probably still stands, that a CMSPlugin defining a render template will always take priority over one defined in the admin subclass API (CSPluginBase)