I played through the game on 'hard' with zero contact with any body who didn't need to be 'neutralized' as per the objectives.
I was surprised when on my next playthrough, I was getting Ghost even though I was knocking people out.
Yeah, their definition of ghosting is a bit loose. It just means that you can't be seen. You can still neutralize every enemy you encounter. While it's cool that you can still genuinely ghost your way through the game, the way XP is rewarded means that doing so will put you at a disadvantage. If you want to get the most XP, there's only one route to go: the non-lethal takedown hacker. Perform non-lethal takedowns on every enemy and hack everything you see, even if you already know the password or have found another way through. They really should have just retained DX's XP system, where you only get rewarded for completing objectives and finding secret areas. That way, there is no inherent benefit to any one playstyle and people can play the way they want without fear of losing out on XP.