I think OP was talking about volleying at the net, that's my explanation.
Technically, you can volley, volley-block and volley-lob from farther back, so maybe reddit should give you the benefit of the doubt.
To clarify: there are varying opinions about slicing from the back, but most experienced players agree on flat/topspin is easier in defense (after bounce) to pull off, you'll make less errors and it's better than slicing. However, balls with certain height above ground from the back can be sliced - as long as we hit 9/10, who would complain about this shot choice.