That's an interesting update. I remain a bit skeptical based on the fact that the obvious sources I'd look to for this sort of thing haven't updated on that study (it seems to be https://www.tandfonline.com/doi/full/10.1676/23-00045), and I'm not really able to evaluate it on my own. USFWS (https://www.fws.gov/story/threats-birds-collisions-buildings...) is citing the previous numbers, as is Wikipedia (https://en.wikipedia.org/wiki/Bird%E2%80%93window_collisions).

FWIW 3.5 billion is not the top estimate, although I'm not sure how to interpret the way the estimate is stated ("annual mortality may be minimally 1.28 billion–3.46 billion or as high as 1.92 billion–5.19 billion"). What does it mean to have a range for each end of the range? The author only quotes the absolute lowest number from the study in press about it (see https://www.lehighvalleynews.com/environment-science/3-5-mil...), but maybe is just preferring to be conservative.