wrong. she can drop a couple different ones as others have mentioned
On average, each act boss has an 18/20 chance of dropping their respective statues, with there being a 1/20 chance of one of the other two eligible statues.
For example, if diriel drops a statue, there is an 18/20 chance it will be a Korlic, with both a 1/20 chance of the statue being either a Talic or a Madawc.