I'm not a native, but have had this dish in Cincinnati, and it is popular in Greek restaurants in Virginia as "Greek spaghetti" and a place called The Hard Times Café in the DC area. It seems to be a matter of choice. Restaurants often sell something called "wet" which is more soup-y (often simply with more of the fat from the ground beef), other's more "dry". It seems to be a matter of choice. I make it every year for my big Christmas party, and I like it about the consistency of a nice Texas chili. My recipe calls for tomato paste, vinegar (only a tablespoon or so) and ... water (I tend to prefer to use beef stock). I just add it until I like the thickness.
Whatever you do, don't use the leanest cut of ground beef. it just doesn't taste right. For me, ground chuck, I think I get 80/20 -- or is it 85/15 -- for the most flavor.