I know it should get easier through each one as the first is most fortified followed by second etc, but at some point they should just be into unfortified areas?
But rumors seem to be that the 1st line was where the Russians put most of their effort into. The fact that the 2nd line of defense might already have a breakthrough proves this rumor.
The 3rd line of defense may be worse defended than even the 2nd line. So Russians may be failing at elastic defense (the 2nd and 3rd lines are supposed to be harder to take, because you can move troops and "react" to how the enemy works vs the 1st line). So this is a very promising development, if the lines get "easier" instead of "harder" to breakthrough, then the 2nd and 3rd lines almost don't count at all.
Satellite photos showed the 2nd and 3rd lines were massively more fortified. Huge anti-tank ditches, concrete bunkers, millions of dragon's teeth, etc. The first line was trenches and minefields.
Commentators thought the 2nd and 3rd lines would be the true challenge because that would be true for a Western army with air superiority. Minefields basically don't matter to nations that can park an instant air superiority boat off the coast of anywhere and just blast anywhere their mechanised infantry want to cross.
We thought the counteroffensive was going slowly because the Ukrainians just sucked at their jobs. Turns out it's because they were doing minesweeping by hand, with infantry, at night - because the British minesweepers they were given either sucked or, again, relied on the assumption of air superiority.
Now that it's a stand up fight again, lo and behold, they are making quick work of the unmotivated, hungry, poorly paid Russian conscripts - who are pretty much all that's left after Shoigu got everyone competent killed in the farcical invasion.
If you go to https://deepstatemap.live/en and select the little "castle" icon, the site will display all their defensive positions based on recent satellite data.
The movement more than three months into the counteroffensive is significant in that it shows Ukrainian troops have crossed at least the first of three Russian defensive lines and are at or near the second line.
The headline part is probably what you already read. Though their 'Ukraine Situation Report' articles also go go over quite a bit of other things that aren't deserving of their own articles.