I'm just a lowly Bronze, so I suspect by 19k miles, you probably reached the points 'cap' if it had been based on each segment being individual flights. For example, with my 7k miles flown, the equivalent points used on the first flight would be either 119k business or 58k economy...so once they remove that from the 'cap' of 318k or 132k, it has 'eaten' up 40% of points. You can imagine, once the next flight segment 'eats' up as a similar amount, and then the next one does the same, that's probably why they couldn't refund any points, since they've all been 'eaten' up based on their individual rates.
Not exactly a 'pro-rata' outcome, but I think that's where one with a significant;y-flown OWA can go down the TI insurance path like you point out, seeing what avenues are available there. As you say as well, retail value could be a great outcome for many too. In my case TI pushed me to push Qantas, who as it turns out, didn't even need much of a push at all. I just mentioned my circumstances, asked what my options were, and was practically offered a refund.