The only angle sensor I ever seen was a tip over sensor to kill the engine and that's basically just a switch.
Never have seen the cruise control hold it rock steady, it tends to drift a mph or three on road conditions, grade etc.
How steep is this curve you are going on?
If you are leaning into a curve you are shifting the weight distribution / traction a bit, so it might just be a physics thing, gravity is acting more on the mass .vs. the fixed power input etc.
As for TC taking over and doing it, I don't think that would do it, and if TC did intervene wouldn't you get some sort of notice on the dash? Anytime I hit a big bump or something that caused tc to do something it always blipped on my dashboard lights.
Just my thoughts.
Aaron