I wonder how Michael Collins and the post-production supervisors could miss something as simple as that.
The line, "Except crime!" at Auric Stud is one example, but more obvious is the dialogue spoken just after Bond escapes from his cell. Goldfinger's line, "The underworld will rock with applause for centuries" is Fröbe's original voice, as is the line, "It can be, I think the expression is, blown!"
More interestlingly, I was watching a comparison between the original mono mix and remix of Thunderball, and found something interesting: On the original mono version of Thunderball, the original voices of Adolfo Celi and Claudine Auger were left alone.