Not according to the 68 SS manual that I have, the only way to get the valve cover off with the motor in the car was to hammer the snot out of the right side inner fender. Have an acquaintance that worked in the facility where the HEMI cars were put together, and he told me they were hammered. Seen someone mention that wedges require it as well, have had a couple of big block a-bodies and none of them needed the inner fenders hammered.
from what i have read. you might be correct on the part that you had to hammer them to get off. but not hammed at the install. i like to see a factory picture. before anybody owned the cars.