The current management are there because they either share the government's position or are suitably obedient to toe the line.
In that vein, they have been strongly supportive of the Coalition's plan and just as strongly critical of Labor's version. They have nailed their colours to the mast and can't afford to back down now as to do so would reflect very poorly not only on themselves but on the Government that hand-picked them.
Whatever the real story, one thing is certain and that is that the NBN Co board are every bit as partisan in this matter as the Government that game them their expensive seats and so one must expect spin and rhetoric at every opportunity. (And the same may well have been true for the last version, but this is what we have right now.)
Saying that NBN Co is independent (and therefor trustworthy) when they have their board appointed by the political incumbents has the same ring as News Corp claiming their outlets are neutral and unbiased when their editors and major opinion contributors* are chosen to match the current political leaning and aims of Murdoch.
* - Think Andrew Bolt and Miranda Devine as recent local examples.