I couldn't find any documentation explaining on this specifically (classic Microsoft)

But it appears if you set nMinPage to 0, and then nFromPage, nTomPage, & nMaxPage to 0xFFFF
the dialog behaves the way you want it to for "All Pages" and "Page Range"
Plus, it appears you need to pre-set the flags to both "PD_ALLPAGES | PD_RETURNDEFAULT"
in order for the dialog to not appear and have the "::PrintDlg(&prntdlg);" call return.
Bug 61075 r=dcone sr=attinasi

gfx/src/windows/nsDeviceContextSpecFactoryW.cpp

@@ -155,10 +155,10 @@ NS_IMETHODIMP nsDeviceContextSpecFactoryWin :: CreateDeviceContextSpec(nsIWidget
     printService->GetHowToEnableFrameUI(&howToEnableFrameUI);
   }
 
-  prntdlg.nFromPage           = 1;
-  prntdlg.nToPage             = 1;
-  prntdlg.nMinPage            = 0;
-  prntdlg.nMaxPage            = 1000;
+  prntdlg.nFromPage           = 0xFFFF;
+  prntdlg.nToPage             = 0xFFFF;
+  prntdlg.nMinPage            = 1;
+  prntdlg.nMaxPage            = 0xFFFF;
   prntdlg.nCopies             = 1;
   prntdlg.hInstance           = hInstance;
   prntdlg.lCustData           = (DWORD)howToEnableFrameUI;
@@ -171,7 +171,7 @@ NS_IMETHODIMP nsDeviceContextSpecFactoryWin :: CreateDeviceContextSpec(nsIWidget
 
 
   if(PR_TRUE == aQuiet){
-    prntdlg.Flags = PD_RETURNDEFAULT;
+    prntdlg.Flags = PD_ALLPAGES | PD_RETURNDEFAULT;
   }
 
   BOOL res = ::PrintDlg(&prntdlg);