I agree. I can't find a correspdonding ApplicationGlobalConstants. I suggest filing an IR with GTAC to get it added.
Regarding StartCommand(), glad you found an alternative. Always avoid StartCommand() when possible. It does though sound like you're saying that SheetWindow.Paste() does not honor the "Preferred 2D Paste Behavoir" setting. If that's the case, then again I'd say file an IR with GTAC to get it reported.