So long as they were uploading less than they were downloading, then they would effectively be slowing down the downloads of others, rather than contributing to them, as the bandwidth of those they were downloading from would not be available to others during that time.
The real concern would be what they were doing with the downloaded materials, not so much how they acquired them. The rights holders honestly don't care that the company downloaded a copy of their book without paying for it. They care that the company trained an AI on their book, potentially allowing for the creation of competing works based on it. The piracy angle is just a means to potentially seek damages against them and deter others from doing something similar, but you can be sure they would be doing everything they could to seek legal damages against them even if they had paid for each book in full.
That's a poor analogy though, as stealing from a store has a direct negative impact on the store owner. The store already paid for the merchandise, so it getting stolen puts them at negative profit that will take multiple other sales to recoup. It also potentially causes them to lose a sale if the product ends up going out of stock as a result. Whereas a file getting copied only results in a potential lost sale to the person receiving the copy, who in most cases probably would have never bought the product to begin with if the only alternative was paying for it.