I think you are conflating “exposure lock” with “exposure compensation.”
As I noted above, when you are in a shooting mode where the camera is controlling one or more legs of the exposure triangle, then exposure settings are recalculated for each and every shot.
Exposure Lock means that exposure is locked, so that you do not have to keep a button pressed to maintain the current exposure. This only lasts until the shutter is fired.
Unlike an exposure lock, however, Exposure Compensation is maintained from one shot to the next. If you wish for your exposure settings to remain unchanged, then I suggest that you use M mode, not Av.
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