The problem was that the bill was not withdrawn. There was widespread legal consensus well known to protesters that “shelved” bill could be reintroduced in Legco at a moment’s notice. The bill was eventually withdrawn but by that time the protests have exploded and there was a lot of bad blood between protesters and police. In alternative history, if the bill was simply withdrawn when government decided to do a u-turn, there was a significant chance that the protests would run out of steam and deprive the more radical elements of momentum. Shelving the bill was a tactical mistake in hindsight and officials say it off record.