It’s in the thread above, and I don’t understand it 100% that’s for sure, but I’ll take a layman’s stab at it.
So when you lase what happens is the bomb guidance unit detects the termination point of the laser and the fins snap to attention and try to align to the target indicated.
I believe bomb fins are set at maximum glide when they are loaded on the pylon and your fire control computer expects that to be the case upon release. So, when you lase early and cause the fins to snap to a different position that would introduces additional drag into the equation. Just like if you pitch up in a plane. When you pitch down in a plane you do gain speed, but there’s an optimum glide slope so if you pitch too far down, and you have no engine thrust, you have just reduced the maximum range you can glide.
Also, I suspect that in RL, when lasing, the bomb tries to fly a flattened curve to the target. So, once again if you trade-in altitude for a line-of-sight flight path and the line of sight flight path is below the optimum glide path, well you never get that altitude back for your bomb, so it’s range would be gimped there as well.
Additionally, keep in mind the fire control computer had no way of knowing that you were going to manually lase early, so it can’t account for that. I’m guessing in RL you want to drop well within the staple if you plan on manually lasing all the way down.
But honestly, I don’t know for sure about any of what happens in real life. I only know what happened in my testing of the sim. So going back through the thread will probably be more enlightening than listening to me.