Cannot add 'Page Title' and 'Main Content' blocks to panel Configuration:


Drupal 8.1.5
Panels 8.x-3.0-beta4
Page Manager 8.x-1.0-alpha23
Layout plugin 8.x-1.0-alpha22
Panelizer 8.x-3.0-alpha2


When I create a Panel variant for /node/{node} with Page Manager, I can add field blocks, like 


entity_field:node:title
entity_field:node:body


These get rendered.

However, if I add blocks 


CORE / Page Title (page_title_block) 
SYSTEM / Main page content (system_main_block)


these render to nothing.
Can someone explain why?
Answering my own question after I found some more info. 

This is indeed a bug, hopefully to be fixed soon: https://www.drupal.org/node/2626090