It worked well in the Mueller investigation. The Mueller Report made clear that critical witnesses refused to cooperate with the investigation.
There is a reason why Trump buries phone calls with foreign leaders in a code word protected vault. And no, it has nothing to do with national security issues.
Re Ukraine, Trump’s play is to delay, distract, and deny deny deny, hoping to exhaust the public’s appetite and attention span for the impeachment inquiry.
Transparency = Death for Trump. Anyone who does not appreciate the real reason Trump seeks to bury the communications and stonewall its production, is a dupe.