I frequently see the "Grand Juries aren't 'fair' either, so screw the Republicans on Schitt's Committee" argument being applied, but I want to see it clarified if this really is analogous to a Grand Jury. A Grand Jury is a very specific thing, mentioned in the Bill of Rights.
Can a House Committee Chair unilaterally declare the Committee a "Grand Jury?" The 5th Amendment doesn't say anything about the composition of a GJ, just that there must be one to be charged with an "infamous crime."