Rule XI says clearly that they can ONLY hold secret meetings if they believe the witness will be degraded or incriminate himself and they can only hold executive meetings if the information disclosure would violate a law or was National Security..
-Republicans want to degrade them, no doubt.
-And some CLASSIFIED info could need redaction
This is an inquiry, the evidence gathering stage of impeachment....
The Kenneth Starr investigation stage
The Archibald Cox investigation stage, both done in secret.
Clinton and Nixon had not been impeached yet, had not been indicted yet.
This inquiry is the committee Investigating, gathering evidence, before they decide what indictments they may charge the target with...
Before any indictment, before any Articles of Impeachment are drawn.
Do y'all really want to charge a person, then go and gather the evidence later to see if you can support the indictment?

HECK NO,
Yet THAT is what you are screaming and whining for....
You want the President to be impeached, BEFORE having the evidence gathered that supports it...
The House JUdicial committee are the Prosectors, when impeachment goes to trial in the Senate