As biomaven noted in a prior thread, the intent of this provision in Hatch-Waxman Section 505(j) is to facilitate rather than hinder FDA approval of generic drugs. Thus, this H-W provision could have formed a basis for NVS/MNTA to have sued the FDA if their ANDA had been rejected on the basis on immunogenicity.
For SNY to argue against FDA approval of generic Lovenox because the FDA asked for immunogenicity data is tantamount to standing this H-W provision on its head, and I expect that the Court will so rule.