I did as you instsructed but the image size did not change--it is still smaller.
MDIJB
After you do what Bart said, select the crop tool, you will now see the area that was previously auto cropped for lens correction, You can then adjust things back to normal.
If you do not want to do lens corrections in the future, click on the little three dots in the upper right hand corner of the lens corrections panel and select Disable Default Lens Correction
Future imports that weren't imported with the lens corrections active should come in without the corrections and crop.