These are not overstocks being sold off, like in the average January sale. These are new titles.
As the article says (I have a sub):
" "To be clear, it’s not a stock clearance exercise," said one publisher. "It’s on frontlist titles out in the last few months. At these levels of discount, no one except [Waterstones] would make money. Not the author, nor the publisher. And for smaller publishers we would actually lose money on every unit." "
At the same time, Waterstones' new order/despatch system, Blue Yonder, remains a shambles. Chief operating officer Kate Skipper told The Bookseller: "much higher volumes of stock have been dispatched this month." She admitted, though, the "consistent stability of BY" — the company’s new warehouse technology provider— "remains disappointingly elusive".
I don't know about you, but if I worked for W I think I'd want to see that sorted first before turning up the heat on long-suffering publishers with reduced price requests. They are, after all, still being asked to supply W orders direct-to-store, at their own expense, while Blue Yonder's operational reliability remains "disappointingly elusive".