All looks fine to me. The first flight has you in row 33 back where it is 2-4-2 (premium economy with a mild refresh); the second flight has you in the economy cabin, with the plane being laid out F-WTP-CW-Economy (and fewer business class seats) so, although the row numbers are higher, the seats are laid out 3-4-3.

It's worth mentioning that the earlier 747 flight to DC will feature updated in-flight entertainment and re-covered/re-cushioned seats, as well as different row numbering - but that's not particularly helpful if you want to spend time in London during the day.