Update: I found the 3x3 mode, which is presumably what the "9 times more fun" message was about, though it's not documented anywhere I've been able to find - the IC2 Wiki, the official FTB Wiki, and the unofficial FTB Wiki all have pages about the mining laser, but none of those have been updated to explain how the 3x3 mode works.
Also, I did some more detailed testing of the penetration distance of horizontal mode in the two different versions of Minecraft (using IC2 2.2.826 and 2.6.81 respectively), and I've looked at decompiled code for both versions. I think the 1.7.10 version goes by blast resistance, and 1.10.2 goes by hardness. However, looking at the decompiled code, I don't understand how it ends up digging so far through sand in 1.7.10, or why this was changed for the 1.8 builds, while it had apparently been left alone for so long in the 1.7.10 builds.
Sand (2.5 blast resistance, 0.5 hardness)
1.7.10: 62 blocks broken, 57 collected
1.10.2: 15 blocks broken, 13 collected
Netherrack (2 blast resistance, 0.4 hardness)
1.7.10: 71 blocks broken, 60 collected
1.10.2: 18 blocks broken, 17 collected
Grass Blocks (3 blast resistance, 0.6 hardness)
1.7.10: 55 blocks broken, 49 collected
1.10.2: 12 blocks broken, 11 collected
Dirt (2.5 blast resistance, 0.5 hardness)
1.7.10: 62 blocks broken, 55 collected
1.10.2: 15 blocks broken, 13 collected
Iron Ore (15 blast resistance, 3 hardness)
1.7.10: 15 blocks broken, 13 collected
1.10.2: 2 blocks broken, 2 collected
Stone (30 blast resistance, 1.5 hardness)
1.7.10: 7 blocks broken, 7 collected
1.10.2: 5 blocks broken, 4 collected
Cobblestone (30 blast resistance, 2 hardness)
1.7.10: 7 blocks broken, 7 collected
1.10.2: 3 blocks broken, 3 collected
Bricks (30 blast resistance, 2 hardness, but blacklisted for the laser in 1.7.10)
1.7.10: stops laser
1.10.2: 3 blocks broken, 2 collected
Obsidian (60 blast resistance according to IC2 wiki (changed from vanilla 6000), 50 hardness)
1.7.10: stops laser
1.10.2: stops laser
Glass (1.5 blast resistance, 0.3 hardness, but seems to be handled specially)
1.7.10: laser passes through, and can break blocks beyond the glass without breaking the glass
1.10.2: laser passes through, and can break blocks beyond the glass without breaking the glass