I’ll share the docs I’ve found while trying to get WinLink working with my AT-d578UV.
The ‘SignaLink USB with AT-D578UV’ specifically advises to use back speaker jacks and not front mic jack for speaker connection so that’s how I built my interface to a Masters Communications interface (before Digirig was selling these fine mobile interfaces). direct conflict with the manual that you have correctly pictured.
AnyTone D578UV Alternate Microphone Mode with Signalink Setup.pdf (776 KB)
SignaLink USB with AT-D578UV.pdf (93.2 KB)