I think this speed is autoselected when first starting mod or when using Play now! (Play a scenario) option in single player menu.In the game, where is it telling the player that this is the default? And what does this bit of XML do exactly?
It looks like all it does is emergency in case some gamespeed was deleted to prevent breaking savegames.
CvInitCore.cpp
m_eGameSpeed = (GameSpeedTypes)GC.getDefineINT("STANDARD_GAMESPEED"); // NO_ option?
and XMLLoadUtilitySet.cpp