Not worried about it. Horowitz has already delivered and moved this thing forward. Most of his report will be/is known by the time it comes out. Wray, for example, said he relied on the IG's finding in regard to moving McCabe along. The IG is the one who outed Strzok, the IG produced the text messages when the FBI said they were gone, and so on.
Actually, we don’t have any statements or reporting from Wray directly. The failing New York Times reported “witnesses” made the connection between the IG and Wray. Not saying it’s not true, just not confirmed.
It’s entirely plausible Wray went to the IG looking for a reason to move McCabe, didn’t get one and decided to move him anyway.