There is often great news that doesn't drive bitcoin prices up. We can't know the exact effects as we can't repeat the experiment.
However, basic economics and monetary theory, and numerous historical examples, both even discussed in the book "The Bitcoin Standard" itself, explain that the Stock vs Flow of a currency defines its hardness.
Suddenly halving this ratio (or inflation rate), instead of smoothly doing so, seems like an notably sub-optimal configuration that negatively affects an important property of good money - stability.
How do you know that the sudden halving of the block-rewards doesn't affect additional volatility?
it does affect the volatility but it is not the only reason and it definitely is not the biggest reason. in other words even if distribution of supply had another model the price would have still been moving in the same roller-coaster manner.
for example price didn't go up to the moon in 2017 because the reward was halved a year ago! it went up because some big countries like Japan adopted bitcoin as a currency and many other countries started having similar friendly regulations towards bitcoin. additionally we finally had a scaling solution for bitcoin be implemented. and like always because the media was talking about bitcoin nonstop! that was a process to speed up the demand and that caused the spike which would have happened even if reward was different.