It is... I did soooo much research on these guys and have found people are really divided on the issue. I have gone to reptile forums where people scolded you if you used sand and forums(like this one) where people use sand with great success. I have been keeping mine on sand for about 5years now and obviously have no problems. But I know people who have kept their leos on sand for 10+ years with no problem. Then there are those people who have had leos die after only a couple of weeks on sand. It comes down to responsibility and how you feed IMO. I feed my leo from a bowl(hate crix!) so there is like no chance of impaction plus she is a full grown adult. I think most people would agree young leos should not be kept on sand.
The other argument is that because these guys come from Pakistan, their terrain is compact earth and not loose sand but Pakistan does have loose sediment as part of its geography so that's a very invalid argument. Use common sense and you should be fine with it. It's just like when that one guy on kingsnake years ago claimed that a mealwrom burrowed out of the waxy's stomach and suddenly people claimed you had to cut the heads off mealworms to feed them to small reptiles. Give me a break. I like sand it is easy to clean and looks very natural and I don't think my leo minds it either .
I recently talked with a veteran from Afghanistan and he said that the substrate I use in my tank was just like what he encountered in the middle east and he had also seen leos in the wild. I use a 50% sand, 25% coco fiber, 10% dried topsoil, 5% small particle desert gravel- just a rough estimate of course but that's probably pretty close to the percents. I don't have any impaction issues with mine I'm trying to find some clay soil to mix in so her burrows will hold since she love to dig when I give her a tub of coco fiber and moss mix to shed.