You are getting confused between what are called Exchange Traded...

You are getting confused between what are called Exchange Traded Options ( ETO's) and ordinary company share options ( such as IBXO an IBXOA). Ordinary company options are 1 for 1 with the fully paid shares. That is, convert 1 option and you get 1 share. The ETO's on the other hand can equate to a 100 of the fully paid shares. ETO's are specifically limited to only some of the major ASX50 top stocks such as BHP or the big 4 banks etc and to trade them the trading platforms such as Commsec and I guess CMC require your account to be specially authorized.