I presume you’re referring to the 2009 thread about “labeling discussions” starting with #msg-43193638. There’s never been another generic drug like Lovenox, so it’s hard to generalize about the FDA review procedure; it would seem to make sense for discussions about substitutability to come near the end of the review process, but they could conceivably come at any time.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”