Currently the option "Update the content of posts to use the new sizes" is disabled because it didn't work properly. It needs to be fixed and then enabled again.
The option was disabled here: 6d4300d
More details of the issues: https://wordpress.org/support/topic/images-replaced-in-posts-all-wrong/
Currently the option "Update the content of posts to use the new sizes" is disabled because it didn't work properly. It needs to be fixed and then enabled again.
The option was disabled here: 6d4300d
More details of the issues: https://wordpress.org/support/topic/images-replaced-in-posts-all-wrong/