I can only confirm that there seem to be some issues with themes behavior in latest 2.3 compared to 2.2. This may have something to do with how Moodle decides whether the pre and post regions contain blocks. In my case, blocks on front page are in a center region and hidden from everyone but admin. When admin logged in the blocks appeared in post region (right column) and it took admin a page refresh to get them rendered in the center region. I removed the pre and post region from the theme frontpage layout so now the blocks do not appear at all after login and it takes a page refresh to get them on the page. Firefox and Chrome.
Blocks
Docking causes all block to vanish in 2.3
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