KET
UMAT had its beginnings in the high dropout rates for medicine and related courses. Too many students with adequate academic performance were either deciding that medicine wasn't for them after all or proving not to have the interpersonal skills and non knowledge based attributes to required of a medico.
Adelaide Uni developed a screening process to assess aptitude for the profession, to complement the academic requirements. It led to improved completion rates. However, quite a few people complained, as their kids weren't getting into medicine, even though they had high ATAR scores. Not the least were some prominent doctors who wanted their children to folow in their footsteps - something I had been told was one of the problems with poor completion rates (medicine was the parents' ambition for their child, not the child's wish for himself or herself). The test was modified and I believe led to the UMAT, which was adopted by universities more widely.
This is my somewhat fuzzy recollection of conversations with a past Dean of a couple of the medical schools, in the late 1990s. The link to the UMAT may not be as direct as I've understood it to be.