Very interesting. I wonder why we get some junk species here and not the really good ones?
The paniculatum and australe and smithii have been in cultivation as ornamentals for a long time, and are suitable for Southern and Inland Australia.
Some others are more recent introductions, first as ornamentals and later as edible "bush foods".
Many Syzygiums are from NTH QLD and Cape York. Most can be moved south, particularly those from the tropical highlands. A few prefer the Wet Tropics only.
Many of these are probably not well known till recently.