I believe he actually said that the contact lens will flatten the eye out a bit, but I'm not convinced I heard him correctly.
That part is true, the lense slightly flattens the eye and can alter your uncorrected prescription. I found that, when swapping regularly between contacts and glasses, I needed a slighly different glasses prescription & when I needed my "natural" eyesight to be tested, I was told to leave off the contacts for 10 days first.
I had a reasonable degree of astigmatism, and my contacts completely corrected it.