I think Barr and Durham are driving the bus; and putting pressure on Horowitz to finish up his report in short order. Horowitz was being stonewalled by FBI Director Wray and the CIA Director Haspel, which is why Trump has given Barr broad authority to force them to disclose the information he wants.
I think Barr and Durham gave Horowitz the facts of life. "If there is any falsified evidence, or evidence you hid/destroyed evidence in this report, you will be investigated next. Feel free to correct any mistakes or oversights you may have made so far, and have it done by July."