«لو» is not restricted to a plain historical counterfactual. In «لو ترى» (if only you could see), an anticipated scene may be displayed with the vividness of direct observation.
«وَلَوْ تَرَى إِذْ وُقِفُوا عَلَى النَّارِ»
If only you could see when they are made to stand before the Fire. (Qurʾān 6:27)
The future scene of judgment is represented as something the hearer might witness. The forms «إذ» and «لو ترى» give the depiction a force beyond a detached predictive statement.
The source’s commentary also treats the understood consequent and the temporal presentation. The suspended construction lets the hearer imagine the gravity of what is being witnessed.