While you are no doubt correct I would have taken it to an election. Labor managed to convince a lot of people to withhold their vote over the cost of the plebiscite. I still believe the actual figures are closer than came out in the vote.
The thing is if the government had chosen to make this an election issue, it’s most likely that the Coalition would have lost such an election. That is why Labor was so intent on trying to prevent a plebiscite because to them, this was a clear election winning issue. It might have wound up closer than they thought - but that’s what they wanted to turn the next election into. One fought on that issue and that issue alone.
Even if the Coalition won such an election - and I think it’s possible that they might have - the nature of an election fought over such a single divisive issue would have made it difficult for them to claim a mandate on any other issue and as such a victory would likely be a narrow one, this would effectively lead to a government that was unable to do much.
And Labor and the Greens would have likely refused to accept that the mandate existed even over that issue - they regard this as a ‘human rights’ issue and their policy is that no government can claim a mandate that goes against their version of ‘human rights’.
A government without a general mandate, because it had fought an election on a single issue is basically what happened during the second Howard ministry (1998-2001) when the only thing the Howard government was seen as having a mandate on was the GST because the 1998 election was seen as having been fought solely on that issue (which was more or less true). Thank heavens, Kim Beazley was Leader of the Opposition at the time, and managed to get the ALP to support the intervention in East Timor because otherwise the Howard government would have been basically paralysed during the most significant policy and defence crisis we’d faced in thirty years. Beazley was a rarity - a moderate/centrist non-socialist Labor leader who understood the core issues of defence/national security and foreign affairs and was generally willing to support the government on those issues.