As in it not a perfect sphere, or as in it is actually flat and not round?
It's close enough to a perfect sphere most every one can go on believing it is with little real consequence. Sure those who we depend on for navigation devices and such (e.g. GPS) need to know the exact figure.
In other words I wouldn't call it lie, just a generalization. It's like saying the earth is 93 million miles from the earth, when that figure is really rounded off to the closest million miles.
Now if you were saying implying it is really flat you probably did so TIC and I should have just chuckled.