BIS_fnc_spawnGroup does not work with a number of units passed instead of an array of classnames. I looked into why and it is because BIS_fnc_returnGroupComposition is outdated with old ARMA 2 classnames.
It's not that big of a deal but it obviously can't be more then a 20 second fix to update the classnames because a lot of people like to use:
[position,EAST,6] call BIS_fnc_spawnGroup
to spawn in a fixed number of units without knowing the classname.