The meeting was at 11 AM, but I said noon in a post/chat/something since anything can change and people don't need to know every exact detail, since they love to tie you to it.
Just a lot of things hitting the main thread leading to spikes. I've spent the last year occasionally hunting the spikes and reducing them. A big one was chunk collider mesh baking, which now happens on a separate thread.
CM now causes certain blocks to not reduce in count, which makes it easier on POI designers.
CM is off by default, but if player does not wipe all their files, it could cause odd issues.