Quote from trader42:
the CBOE page
http://www.cboe.com/TradTool/Symbols/SymbolDirectory.asp?MODE=IndxOptsNLeaps&POPUP=false
does specify "Broad" for QQQ options too ...
Yes, it does, I agree. However, if you scroll down a little more, you will see that "Broad" is defined as...
Broad = "Market" Index (Lower Margin Requirements).
The key phrase here is "Margin Requirements".