As many economists have pointed out, sustainability concerns have to be addressed at a fiscal level. This means that the debt-to-GDP ratio has to stabilise, and those projections need to be realistic. If debt sustainability can be assured, with high probability, then near-term borrowing will be more readily available.
In these circumstances, were government still to experience financing disruptions, we would feel confident that these were liquidity problems which the SARB could help address. However, presently, sustainability is not assured, which makes large-scale sovereign bond buying potentially inflationary.