Yeah, that option was specific to the directx version of Zerogs. This looks like the only code that used it:
if( g_GameSettings & GAME_RELAXEDDEPTH )
SETRS(D3DRS_DEPTHBIAS, g_nDepthBias?FtoDW(0.00003f):FtoDW(0.0001f));
else
SETRS(D3DRS_DEPTHBIAS, g_nDepthBias?FtoDW(0.0003f):FtoDW(0.000015f));
And it's clearly DirectX only...
Edit: If you look at AlphaSetDepthTest in ZZoglFlush.cpp, that commented out SETRS command is where that code was previously in the DirectX version of ZeroGS...
if( g_GameSettings & GAME_RELAXEDDEPTH )
SETRS(D3DRS_DEPTHBIAS, g_nDepthBias?FtoDW(0.00003f):FtoDW(0.0001f));
else
SETRS(D3DRS_DEPTHBIAS, g_nDepthBias?FtoDW(0.0003f):FtoDW(0.000015f));
And it's clearly DirectX only...
Edit: If you look at AlphaSetDepthTest in ZZoglFlush.cpp, that commented out SETRS command is where that code was previously in the DirectX version of ZeroGS...