I have been to the Mt Tambourine area a couple times. Also I lived in Nth NSW for a short time.
The wild diversity of fruit size, skin colour, pulp colour, flavour combinations is very large.
If you look at a website of cultivated types, you are seeing mainly larger fruiting types, with clean skin / pulp colour combinations.
Also nice flavours are selected. The wild flavours range through lime, lemon, grapefruit, berry, etc
Smaller fruiting types ( more common ) aren't collected. Also some wild types have very sour fruit, not pleasant.
Many people live adjacent to the rainforest in both areas, and simply found large fruiting Fingerlimes on their property.
Others must have actively searched them out.
There have been a few disputes about who found what, etc.
Sadly there have been extensive bushfires in the NSW/QLD border Rainforest areas in the last few years.
The wild diversity of many species has been threatened.
Another interesting question is why are Fingerlimes so variable ?
Obviously the fruit must attract something for dispersal. They are similar colours and shaped to many fruit eaten by the Nth Qld Cassowary.
A fossil Cassowary species has been found in NSW, but they no longer occur outside the Wet Tropics and Cape York and PNG.