He would not want you to correct his original work which he compiled from the actual registers, by using the official index entries to do so. It is illogical.
It should be corrected from the registered entries, or not at all.

That is why I suggested putting the entries from the official index into a second FHS index, to keep them apart from the ones Brian compiled from the register.
He would expect you, and anyone else interested, to add to his work, not to damage it.

Sue