Yes :-) The svgLinkTarget parameter has been implemented quickly and badly.
If you are using SourceStringReader class, when calling generateImage(), you currently should pass a FileFormatOption argument.
And build this argument this way:
new FileFormatOption(FileFormat.PNG).withSvgLinkTarget("_parent");
We'll try to refactor our code so that this workaround is not need anymore.
Hope it helps!