PR after 2 years as resident sells house in country of origin. Proceeds from the sale remitted to Australia, would it be taxed ?

In sufficient information. Selling a house doesn't necessarily create a tax liability. The difference between the sale price and the original purchase price is generally where any tax calculation START.

If it was, it would be as capital gain.

It would be if he were a resident the entire time, and it wouldn't if he weren't.

So my guess isb hat it would be taxable from the time he was a resident.

But why not ask an accountant? I'm just a heroic legend with a big dìck, not an accountant.