That article went past my level of expertise, which suggests that "easily" is, as you imply, a matter of perspective. It's possible the current behavior is a result of tradeoffs made for performance or cost. Modifications to make the model deterministic could depend on making unacceptable tradeoffs.
For the curious reader: https://news.ycombinator.com/item?id=37006224
It appears that it could "easily" be made deterministic.