I realize that development discussion is supposed to go to openldap-devel, but despite having subscribed to that a month ago, none of my postings have gone through. I hear they are having some technical difficulties with that list, so for the sake of this submission not being indefinitely delayed, here it is.
Attached is a proposed patch to fix ITS #7161. It uses the same method as the accesslog module to generate a subsecond generalized time, appending the o_tincr value from the operation structure as fractional seconds. The only other code that looks at the value of that attribute calls parse_time to pull seconds out of it (ignoring the fractional second part), so other than modifying the format the attribute is stored in I don't believe there are any other changes required with this.