I will just say that I have recently found that if I purchase my own title, and then I purchase another title related to my book (and I did this out of genuine interest)--to my surprise, the title of the other book appeared in my "also bought" list! It was easy to tell cuz my Also Bought list is still very small. So, yes. You could try this.
I had heinous also-boughts COMPLETELY unrelated to my book before I ran my promo.
After the promo, the also-boughts are much, much, muchmuchmuchmuchmuchmuch better. However, I am unsure if this is from like-downloads, or the boost in sales that occurred immediately after the promo.
Before my promotion, my also-boughts were books geared for making great birthday cards and coping strategies for widows. My book is like a high-intensity, 80's action flick, in pure nose-breaking, gun-slinging, manly wrestling glory.
Ultimately, increasing my visibility corrected that.
If you give away a BUNCH of free promos it will temporaryily boost the coustomers who bought... also bought... listings
BUT those listings may be useless because the people who take most of the freebies grab anything. I remember one scifi author complaining after a hugely 'successful' giveaway, his book was mostly showing up on pages that featured free cookbooks. I have nothing against cookbooks, but that's not exactly a scifi author's target audience. As I said, the book takers will grab anything free. And most never buy a book.