All the incorrect variant forms of a heading will be replaced by the standard, authorized, correct form. There are over 2 million headings in BobCat. Authority processing should merge several hundred thousand of the variant, incorrect headings into authorized headings.
Some variants are due to changing cataloging rules over the years.
Our efforts to quickly convert almost one million manual records in the 1980's did not allow us to carefully review and update all headings. It will take two successive record loads to eliminate incorrect headings and provide legitimate cross-references to correct headings. This sounds complicated. Yes, it is complicated, and, No, we are doing our headings clean-up differently from other libraries. The structure of the Geac database, with its separate but linked authority file allowed us to just send out a file of our headings rather than a copy of the entire bibliographic record.