I doubt the president of the United States would be so quick to grant a full pardon to the Flock CEO for any past (or future) crimes committed.

Thanks for proving my point.

Do you genuinely think this is the only case of a government bureaucrat being called to testify before Congress?

The current President would be happy to give Flock's CEO a pardon, if the price is right. (For example: https://www.newsweek.com/ceo-pardoned-by-donald-trump-arrest...)