The white colonists had interactions with the animals so we can assume that they actually knew what they were talking about so I think you've got a good point.

Interestingly the story of the Thylacines extinction starts a lot earlier than white settlement.

"The fossilised remains of thylacines have been found in Papua New Guinea, throughout the Australian mainland and Tasmania.

Factors including the introduction of the dingo led to the extinction of the thylacine in all areas except Tasmania about 2,000 years ago. The thylacine population in Tasmania at the time of European settlement is estimated at about 5,000."[0]

0 - https://www.nma.gov.au/defining-moments/resources/extinction...