TO speeds are calculated with the Actual TO weight. The TO speeds have nothing to do with the thrust setting for TO.
The speeds are designed for aircraft weights, Thrust settings have a minimum for a certain weight (your assumed) but can be increased for different reasons (fog, CB's in vicinity, slippery runway, ...)
For example, light aircraft on a foggy runway.. Full Take Off thrust is mandatory to get you in the air as soon as possible. Which idiot would use higher speeds, and make life difficult with staying on that foggy runway, or in the worst case having to abort a take off at a critical point near V1 with all the hassle of keeping the aircraft at high speeds on the runway, while lower speeds are available??
BRGDS,
Tuur