In most builds using Cyclone / GNG etc motors, the motor does not drive the bottom bracket itself.. it drives a chainring that rotates around the bottom bracket but does not apply torque to the bottom bracket.
So yes, in a "normal" setup the only torque the bottom bracket will see is the torque applied through the pedals, and the system will work fine.
Good on you for thinking about using Torque Sensing: for off-road riding it is far superior to "Normal" PAS / cadence sensing control, and gives a very natural, instinctive riding feel and a safer, more rewarding riding experience (assuming it is well set up, of course).
Although not commonly advertised, Sempu can make a T3 model torque sensing bottom bracket which works with ISIS crank arms instead of Square Taper. Electrically and dimensionally it is said to be identical to the T4. If you would prefer the ISIS version and cannot find it for sale, PM me and I will send the link to a supplier willing to get one (on Aliexpress).
Good luck with your build.
Dave