The S-3 Amendment was made in order to re-file the legal opinion provided with the original....certain required information was left out. The changes added 9-10 word phrases to the ends of paragraphs 3, 4 and 5 which are critical for legal purposes but unimportant to regular people :o)
The only thing that I wonder about it is, who caught it? While the theory is that one sets up these shelf registrations for some future use, I don't think that they generally just hang there in limbo for an extended period. I think that they are set up to deal with an imminent need and THE REST then hangs out. So maybe a new investor caught it. And maybe not.