Lets see some pics of your savannah that was kept like that, its either a fat ball, skinny and dehydrated or DEAD like so many others that are housed the way you describe. Its funny what people think is acceptable, not really though

You need alot of dirt plain and simple, it provides much more then something to dig in but provides humidity and a temp gradient where the animal can escape as well. You wonder why so may people have savannahs yet so may die within the first year and no one breeds them ??? Its because people keep them in crap conditions plus no breeder is going to spend 1000's of dollars to set up a few adults, feed them and then only be able to sell the babies at 25-50 while they are imported by the tens of thousands and sold for 10-30 dollars.