After reading both the IGN article and the WB report, I believe MVS isn’t the entire $100 million loss, but rather a part of it.
According to the report, gaming revenue as a whole is down 31% from Q3 of last year, with the reason cited as better performance of titles released last year around the same time (Mortal Kombat 1 was name dropped here as an example). Now, Multiversus actually launched in Q2 (April - June) but since it’s a live service game, we can count content releases and the PFG acquisition as part of the loss (the acquisition was in July). Additionally, Harry Potter Quidditch Champions launched in September, and I admit I have barely seen any hype surrounding that release (for context, most people were asking for Quidditch DLC in Hogwarts Legacy instead). Admittedly, that game would have minimal impact on the Quarter, but it is worth mentioning as, outside content updates and any mobile games I missed, WB’s only release this Quarter.
So while I don’t think MVS actually lost WB $100 million on its own, I do think it was a cause and effect and that the game contributed to a loss.