IAD to NRT Flight UA803 777 different seat configs?

So I finally booked the following flights

May 16th IAD - NRT - FUK - GPU'd
June 9th FUK - NRT - SEA - IAD - E+

My issue is that the IAD-NRT is showing up on seatguru and seatexpert as a different config from what united.com is showing. SG and SE both show 3 class (BF, E+, E) and the united is show FC, BF, E+, E.

Now I am just wondering if when I apply the GPU and then the seats change to something else will that be avail through the united website? And what site is correct?

Thanks