I know when I installed mine, the length of bolt sticking out of my slider(s) was the same as the bolts they replaced. Of course I followed the instructions and made sure they were equal.
Someone with a true engineering degree knows, perhaps Fred, or someone can look it up.
But if you have say a half inch bolt, and you can thread it in a half an inch and torque it to the thread's maximum torque, that's as good as having it threaded in an inch. The threads only hold so much. So even if that bolt was threaded in further the force applied to it would have stripped out even more of your block.
I went through this back in the day with a Honda Accord that I wrecked and the motor mount was sheared off. The engine was fine, but we were concerned about how deep we could screw the bolts into the motor at the mount as only half of the mount was left.
There was just a fraction over the bolts thickness, in depth available.
We ended up putting another 140k miles on that car after that
without issue.
Now, I'm not saying that these longer sliders don't pose an issue when forces are applied to them in just the right way. Obviously that's not the case. But the roll the dice and takes your chances. I'm keeping mine for now.
Oh, and more importantly, you were OK