This will not scrape off! The high spots have to be knocked down with a floor scraper and the entire surface has to be skim coated and sanded several times, and it’s a shit-ton of work…Source: just did redid this exact ceiling in a 3000 sq ft house. It was weeks of waking up with drywall dust in every orifice of my house and body…also pretty sure some of this stuff is asbestos mixed in, so don your PPE as if your life depends on it, because it probably does.

The other option that was considered was laminating 1/4 drywall with spacing shims, and then tape and texture and paint everything, but when I added up the cost of material and time, I went with the skim coats option. It was 3 weeks of my life, I don’t care to think about; TBH.