I found out what the problem was, and it was not SpriterPlusPlus fault but mine.
Reason was: I use a "model" image to place the different limbs of my animation correctly in Spriter.
However, it becomes useless once in game. So I removed the line "<file id="6" ... />" by hand (back in the day) from the SCML file.
But the current loader is guessing the file id, and not reading it, so all files id afterwards where wrong for SpriterPlusPlus.
That's it. (Reloading the broken file in Spriter and saving a new version fixed it easily).)
@lucid OK thanks, nice new wrappers.
I updated my fork https://github.com/Breush/SpriterPlusPlus with the PugiXml loaders.
You should check example/override/pugixml* and the pugixml at the root directory.
Works all right for me.