"Does this issue only apply to those who didn't register their...

"Does this issue only apply to those who didn't register their shares with a broker back at the time the company moved to the US?"

Yes - I believe so.

You did the smart thing and registered your shares to be held with Westpac at the start.

Next step for those who are contacting AST to identify themselves as the share owners is to move them to a broker...if they want to sell them (at some point), otherwise the shares will just be sitting there in limbo (at least the ownership is confirmed).

That is the way I understand it.