I know that according to a strict interpretation of the RAW it isn't since the spell description only mention club and quarterstaff and makes no mention of greatclubs.
However, considering the nature of human language both clubs and greatclubs are clubs and can be referred to by the common term club. (After all how big must a club be to be called great?)
So I guess the essences of my question is how do we know the game's designers didn't fall in the trap of using a common name for two very similar items because that's the human thing to do?
So is there some precedence where the rules refer to type of weapons as group, such as bows and doesn't specifically name each weapon or vice verse?
After all, like with the quarterstaff the spell doesn't actually boost a greatclub statswise so using one would only be flavor, so excluding greatclubs doesn't really make sense.