Hi, 2020 graduate and UNSW med hopeful here,
To clarify, for non-rural UNSW med, the absolute cutoff for ATAR last year was 99.25 - if you get under this you will not get an interview regardless of UCAT. The median atar was 99.7.
The absolute UCAT cutoff was 90th percentile whilst the median was 97th. The percentile is a better indication as the scores required for each percentile shifted up drastically this year.
UNSW selection is done by ranks; they take your rank out of all the applicants for all 3 areas (interview, atar, ucat), add them then take the top [x] number and give them offers. As such, if you are near the cutoff for ucat or atar, you will need to achieve near-perfectly for the other sections.
e.g: if you get 99.25 atar, you will need a 99th ucat (top percentile) or a very high 98th, if you get low 90s ucat you will need around a .7> atar to compensate.
Source: UNSW open day - they are quite transparent about this (unlike some other unis)
Good luck, hopefully I'll see you there next year!