This is certainly done on the CreateSpace platform, so I assume it's done by the awful KDP Print Beta program as well. As others have pointed out, all pages are double-sized, so you will end up with an even number. And CS then adds another sheet, with the last verso (left-hand) page containing a bar code and printing information. So a 299-page book (counting the front matter) will actually contain 302 pages.
However! It really doesn't make any difference. A few sheets of paper one way or the other won't matter.
(Don't trust KDP to publish a print edition. Don't trust CreateSpace to publish an ebook. Each does one thing well and the other thing poorly.)
I have not read anywhere they add blank pages automatically. Download their pdf book called Print Publishing Guidelines by Kindle direct publishing.
I believe they will tell you the layout in the booklet if you need to add a blank page, but I don't believe they automatically add the pages for you.
Especially because you are paying for each page, they would make that clear along the way. They are counting on you to lay it out correctly and they will not compensate on your behalf.