Understand first that Exposure Compensation (the concept) simply changes how the METER interprets the light it sees in the scene...the meter then biases what it thinks is 'proper exposure'. Point a meter at bride in white gown in a snow field, and it (without EC) will suggest an exposure that renders the gown and snow dingy grey! Use +1.5EV EC and then the meter suggests an exposure that renders the gown and snow more white in appearance.
Above, the three zones of the PhotoVision target...the left shot is exposed per spot meter reading of the central 18% area, the right shot is exposed per spot meter reading of the lower white area...the difference in exposure is 1.66EV more exposure on the left than on the right. The left shot was exposed at 1/25 f/4 ISO400, while the right shot was exposed at 1/80 f/4 ISO400.
If I had aimed my meter at the white area at the bottom while in Tv or Av mode, I would need to dial in EC = +1.66EV to tell the meter that "my metered target is actually brighter than 18% gray by +1.66EV". That way the meter would have asked the camera for 1/25 f/4 ISO400, rather than asking for 1/80 f/4 ISO400 while it was pointed to the white area. It changed the meter's interpretation about what it was seeing...it really was targeting white, and not targeting something mid-tone grey.
So EC does NOT make a camera more sensitive to the available light, it merely tells the meter to ask the camera to use a slower shutter speed or larger aperture to render the scene correctly.