You think a Conservative speaker would "cow-tow to attacks from the left" ??
Anyway, a "lie" is somewhat different from "misrepresentation" or "misleading". The government did not outright lie to the public, but they did mislead them which is considerably offensive you when you realize it was a $14 Billion concealment.
And the Speaker's position makes an even better case against the government anyway. We wouldn't want to actually aid the credibility of this government by showing that they selected an honest speaker. That would mean the opposition actually has to do some work.