Update comment on CorePickerUIData

also restore systemid default core restore logic that exists for some reason

src/BizHawk.Client.Common/config/Config.cs

@@ -18,7 +18,7 @@ public class Config
 		public static string ControlDefaultPath => Path.Combine(PathUtils.ExeDirectoryPath, "defctrl.json");
 
 		/// <remarks>
-		/// <c>AppliesTo[0]</c> is used as the group label, and
+		/// All SystemIDs in <c>AppliesTo</c> are used as group label, and
 		/// <c>Config.PreferredCores[AppliesTo[0]]</c> (lookup on global <see cref="Config"/> instance) determines which option is shown as checked.<br/>
 		/// The order within submenus and the order of the submenus themselves are determined by the declaration order here.
 		/// </remarks>

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -107,8 +107,9 @@ ToolStripItem[] CreateWindowSizeFactorSubmenus()
 					{
 						// invalid --> default (doing this here rather than when reading config file to allow for hacked-in values, though I'm not sure if that could do anything at the moment --yoshi)
 						var defaultCore = coreNames[0];
-						Console.WriteLine($"setting preferred core for {appliesTo[0]} etc. to {defaultCore} (was {preferred ?? "null"})");
-						Config.PreferredCores[appliesTo[0]] = preferred = defaultCore;
+						Console.WriteLine($"setting preferred core for {submenu.Text} to {defaultCore} (was {preferred ?? "null"})");
+						preferred = defaultCore;
+						foreach (var sysID in appliesTo) Config.PreferredCores[sysID] = preferred;
 					}
 					foreach (ToolStripMenuItem entry in ((ToolStripMenuItem) openedSender).DropDownItems) entry.Checked = entry.Text == preferred;
 				};