I think your SM is correct
Schedule 2 section 10 says voting can be by any means specified in the notice.
There are no other requirements specified.
Also a special , or any other, resolution can be carried on a zhow of hands or majority of votes carries the motion. Only if a poll note is called fo unit entitlements come into play. The SM will calculate these at the meeting.
The SM can insist that the voting paper sent is the only one accepted. However I would say that as long as the voter is jdentifiable and their owing intentions are clear, their vote should count.