it's not advisable to be dishonest with Commons Committees.
Why? Afaik nobody has been sanctioned for dishonesty to a committee since the 19th century. Either nobody has been telling fibs (unlikely considering the phone hacking people all testified) or its a relatively empty threat.
The headline is a factual summary of what the HMRC boss told the Public Accounts Committee.
If anything what he said is the interesting bit, but it's not advisable to be dishonest with Commons Committees.