An Australian Visitor Visa does NOT Guarantee Entry to Australia.
Getting a Visitor Visa to Australia is not a guarantee that you will be allowed entry.
Some nationalities, where visa fraud or visa overstay is a problem, may also have to convince the Immigration Officers in Australia that they are genuine tourists.
Not everyone is able to do this, and a number are refused entry based on Genuine Tourist Intention grounds. The onus is on the applicant to demonstrate an intention to make a genuine visit.
A recent news report highlights this issue:
Almost one third of Malaysian tourists were refused entry into Australia after landing, between 2017 and 2019.
Some Visa Applicants might find an Experienced Australian Migration Agent of great assistance.