There has to be a sewer somewhere with effluent composed of the political classes. https://thehill.com/policy/national...-will-not-voluntarily-testify-says-his-lawyer
Yeah, all he is saying is give me the cover I need by making it compulsory and I'm your man. He explicitly said he would be available if subpoenaed, that is a clear signal he will be highly co-operative. Being Bolton of course he will find something to be a thorn about but.. he is ready, willing and able. He was the 'grown up in the room' warning about all of this.
Hell, one may say it's a smart move to "oppose" voluntary testimony, as being compelled means he didn't have an "axe to grind". I don't think Bolton is that smart however.
It is not necessarily clear that he will testify even with a subpoena. Bolton's deputy, Kupperman, demanded a subpoena and then refused to appear. His attorney just wanted a subpoena, I guess, to have that as a basis for taking it into the courts. Oh, and guess who Bolton's attorney is???? Yup, Kupperman's attorney.