Were gold(II) complexes synthesized for the first time in 2017?
You are correct in noting that there are a number of Au (II) small molecule species synthesized prior to the report of Professor Katja Heinze in 2017.
The heart of the Au (II) claim by Professor Katja Heinze and team as stated in the article you referenced, see reference 1 given below, has to do with the a) relative stability of the mono-nuclear gold-porphyrin complexes compared to other Au (II) systems and b) that the molecule does not have a Au-Au bond.  The latter point being the more important.
Au (II) is a very stable oxidation state for molecules containing Au-Au bonds.  We synthesized and characterized a number of such species years ago, see references 2 and 3 below for two papers describing the work.
For those working in the field, the nature of the claim by Heinze et al. is understandable.  For those outside the niche field of Au (II) chemistry I can see how the distinction is less than clear.
References
https://www.sciencedaily.com/releases/2017/08/170808145949.htm
https://pubs.rsc.org/en/content/articlelanding/1985/c3/c39850001278#!divAbstract
https://pubs.rsc.org/en/content/articlelanding/1986/C3/c39860000321#!divAbstract