I have seen this a few times, where the usual "close" word is replaced by the word "OK". Please note that everything else works as with any modal, you can click outside the modal and it will close anyways. However, the user intention (to close the modal) is not explicit anywhere.
On further research, I have noticed that this happens only when plugins are installed or WP displays a message, but if it requires some kind of action (like, for example, installing a plugin) the word OK is replaced by X (see below)
My question is: isn't this behavior adding more friction than an usual close or X sign? Is there any kind of studies on this conditional behavior for closing elements?