Why QE green bonds?

Richard Murphy and Colin Hines propose a “National Investment Bank” in the Guardian which issues “Green Bonds” which the Bank of England then “QEs”: i.e. the BoE prints money and buys up those bonds.

The trouble there is that having government or any nationalised institution (like a National Investment Bank or government itself) issue bonds with the BoE then buying back those bonds is that that all nets out to “government prints money and spends it” (sometimes known as “overt money creation” – OMC).  So why not do the latter and not bother with the investment bank or green bonds?

In contrast, I can see the point of green bonds which are not QEd: people with money to spare might be prepared to do a bit for the environment by lending to green projects at a rate of interest below the going rate on bog standard government debt.