Not quite. An ATAR of 95 or above represents the top 5% of everyone who wouldhave been eligible for an ATAR (including drop-outs etc).
Quoted from the UAC 2019 scaling report:
An ATAR of 99.00 does not represent the top 1% of the ATAR cohort; 1.7% of the 2019 ATAR cohort actually gained an ATAR of 99.00 or above. It does, however, represent the level of achievement necessary to be in the top 1% if all HSC-aged people in NSW had completed studies that made them ATAR-eligible in 2019. From Table 4.4 we see that, in 2019, 16.8% of the ATAR-eligible students received an ATAR of 90.00 or above and 33.4% gained an ATAR of 80.00 and above.