To quote the actual report: "This distribution of cases does not necessarily reflect the overall distribution of censorship."
They asked people to self-report instances. There is probably selection bias (maybe they advertised only to the pro-palestian crowd. Maybe the israeli crowd thinks HRW is biased and didn't want to engage. Maybe something else). There is probably also base rate falacy involved which isn't accounted for.
This just isnt the right type of study to determine if meta has a bias in censorship.