I was triggered to write this blog because of a question on Facebook about changing the title of a content type in the content type hub.
I was able to answer this question because I found the same issue a while ago when I was working with the same thing.
The question was: When I create a content type in the content type hub and publish it, the content type is pushed down to all site collections and there you can use it in your lists and libraries. Now if we change the content type’s title or description and republish it, the changes are pushed down to the level of site collection but not to the content types associated to a list. When we create a new list the changes are visible for that new list.
The issues is not only there when you use a content type hub, it is there also when you create a content type on the site collection itself.
To figure out what was happening I went into the SharePoint pages and there code behind with Ilspy. The code I found was that the content type was only updated on the level that you are on (site collection or list)
The update that is triggered does not update its children see the code below
This update gets us into the Content Type class
The false here is that the children should not be updated.
Now why is it that when we add field that they are updated on all levels, this is because we here have the option to update the children like you see in the next screenshot
So the next logical question, is there a work around? I do not think there is. This is because the content type in the list is a new content type that inherits from the site collection content type. If you check the content type ID of the one on the site collection and the one of the list you see that the one of the list is longer like this example
The Content type “New Word” on the site collection level has the following ID: 0x010018F21907ED4E401CB4F14422ABC65304 When I added this content type to a list and checked the content type ID is was: 0x010018F21907ED4E401CB4F14422ABC6530400F1B69D646AC4A343B13C633AE770BE45
This why the title and description are not updated.
I hope this clarifies the working of content types and updates on them.