I can provide context.
The quote's source is Tim Morrison, who is also wrapped up in all this. In particular, he confirmed the quid-pro-quo and
In other wordsalso told House impeachment investigators that he was advised by then-White House official Fiona Hill to stay away from the parallel Ukraine policy being pursued by Trump's personal attorney Rudy Giuliani, according to one of the sources.
a) this is one defendant attacking another defendant, and
b) Vindman responded by reading aloud former top Russia adviser Fiona Hill's final performance review of his work: "Alex is a top 1% military officer and the best Army officer I have worked with in my 15 years of government service. He is brilliant, unflappable and exercises excellent judgment.", and
c) I see Trump has learned nothing. Having the WH tweet instead of him is no less witness intimidation.