That’s certainly not impossible, but it would be a matter of killing the golden goose. More and more Australians make the pilgrimage to Vietnam every year - for many of the veterans in their 70s, they know it’s their last chance and not all have gone for Long Tan - though pivotal in Australia’s time there, to individuals it can be far less important than where they served themselves. And their kids are going as well. Economically from a Vietnamese perspective I’m not sure this makes sense and so I’m not sure that is what is behind it. Seems more likely someone has taken offence at something, whether justified or not and nobody is talking about it right now.
I agree with that. It is a reason, but I don’t it is the “right” (Actual!) reason for this cancellation, nor is it a good, long-term answer - for the very things you mentioned.
If this were Hillary’s government, I would say somebody bought off Hillary. But the North Viets always seemed more sensible than this.