There are some different things included in your discussion here. For example, one point of discussion is the change in the behavior of international students, and another different point is the change in the behavior of admissions committees.
I can understand that international applicants would be concerned, and then some of them would decide to not come to the US. I applied for Fall 2017, so right during the period when Trump was elected, and I saw a lot of people worried. And I also know that there are PhD students preferring to move to other countries after graduating, because of the uncertainties they would face in the US.
So, I guess we can see a reduction in the number of international students because of the changes in the behavior of applicants and students.
But I don't see why there would be a relevant change in the behavior of admission committees. Maybe there is some reason I'm not being able to see, or that I'm not aware of. But I don't expect universities to change policies against international students for PhD applications in business.