For example: Apple Books
When you create a note, the note doesn't have a close button, you click outside and it closes. If you delete the content, the note is automatically deleted. It doesn't have delete and save button because it's all inline and direct manipulation to people can do with speed.
I wonder if this is considered inaccessible ? in order to be accessible, do you really need to create a "CRUD " bulky dialog with the X, a button with save ?
It is a good question. Now, there is a lot of debate around the topic of cancel and close buttons.
Refer to this famous article about close vs cancel https://www.nngroup.com/articles/cancel-vs-close/ for more depth of minor use cases.
In your user case that you have mentioned in the question there are two things to consider.
For any CRUD, it is the conscious action taken by user and it is upto the product to design it to obstruct the user flow or not to. But the close icon given has a lot to do with accessibility as well where in the key sequence is decided to ease the user interaction/navigation.
In the case of Pages, adding a comment is not breaking the user flow with respect to the task that user is doing. It is a optional or addon UI element that opens and close according to inputs given and hench no close icon is given.
Again it is completely customized from product and different use cases considered in comparison.
