Doing a search for RN seats for IAD-HKG flight departing on 9/18 and getting different cabin availability for the same flights (ORD-HKG); changing based on connections.

First flight got this: Available Cabins: F8, FN8, A7, ON4, O0, J9, JN8, C9, D9, Z8, ZN8, P8, PN8, R3, RN3, IN0, I0, Y9, YN9, B9, M9, E9, U9, H9, HN9, Q9, V9, W9, S9, T9, L9, K9, G0, N0, XN9, X9

Second flight got this: Available Cabins: F8, FN8, A7, ON4, O0, J9, JN9, C9, D9, Z9, ZN9, P9, PN9, R0, RN0, IN0, I0, Y9, YN9, B9, M9, E9, U9, H9, HN9, Q9, V9, W9, S9, T9, L9, K9, G0, N0, XN9, X9

Both are for the same flight UA895 ORD-HKG but with different connection from WAS, can someone explain the difference?

Thanks.