UG's are not being slaughtered. What's being slaightered are CPU's. With a bit of picking & choosing I have yet to have a problem booking directly into F with an -UP fare.
The change is that a 1K on one of the deep discounts is beat out by a Silver in B.
I do suspect that IAD is one of those stations where there is likely some abuse of YCA because there are many senior government officials who control their travel directly and indirectly a great deal more than the average GS type.