Hi Gleb, you know me as Bazza from The Quest for Thylacoleo; I'd just like to comment on your question.In the early days of white settlement in Oz people weren't too interested in anatomical exactitude. For example a "Tasmanian Oak" is absolutely nothing like an oak (quercus), but is a eucalypt, pure and simple. Same with a "wild cherry", though that isn't a eucalypt, but is semi-parasitic on eucalypts.
However, I think the real reason for the thylacine's misleading common name of "Tassie Tiger" was that it is more alliterative than "Tassie Wolf". Sure, the thylacine looks like a wolf, but it led a solitary lifestyle like a tiger and had stripes like a tiger. This was all the hook that early settlers needed to give it an inappropriate common name that trips easily off the tongue.