For every increment of the Structure Rating you make a 1-square-meter increment hole. So let's do the math for a second.
Let's assume you lack the skill needed so default at Agility -1. This means probably 2 hits average, raising damage to 18P/-6.
S8A12, versus 18P/-6. This leaves 14 soak dice, which likely rolls at most 7 hits. So you'll have a 1-square-meter hole. If you have decent training and the soak is average or less, you have a shot of making a 2-square-meter hole in a single Complex Action. So that's doable. You'd have to make big enough a hole to properly move through, so 1 Complex Action may not suffice for some people.
A brick/plascrete internal wall will be 10cm, so you would need 2 structure damages for a decent hole. 10/16 means 20 soak dice, average 7. Each attack is likely to do enough damage for 1 structure damage, so 2 Complex Actions.
An external wall would be 30cm, so you'd need 6 Complex Actions (maybe 7) to cut a 2-by-1 hole through.
Here's the important question: Why do you think this rule may be incorrect? It's a clumsy thing that requires training to properly use, makes a lot of noise when used and is impossible to conceal. A GM may also not allow you to default to add bonus damage since it's an exotic melee weapon, so only allowing you to use the base damage (without bonus hits). Granted, that has little final impact but still.
So yes, with this you could easily break through a wall, but you'd set off any and all alarms in the process. Why do you think you may have gotten it wrong?
