They are solid.
Unsure if you can flatten someone by dropping debris on them. Might be a game decision. I'm not sure. I'm not part of the technical test so I can't make my own yet.
Looks like you get damaged if it does fall on you.
As for whether it relates to gameplay. For a lot of gamers, at first glance it doesn't. Most people don't get it. For a lot of players who play these types of games, it does.
If you ever played World of Warcraft Arena, everything is lock on, auto attack. The only way to stop a group from hitting you is to break line of sight, ie hiding behind a pillar.
There is absolutely no other way except line of sight and kiting them out of range of their attack. And team members need to work together to flush healers out of cover, control the attacks etc etc. There is a ton of coordination around it, and an e-sport that eventually died off on it over the past 2 years.
And this game is exactly the same. It has a lock on which is how you fire, since you don't aim. So once you're locked on, you have to break LOS to stay alive. One of those ways is going to be hiding in buildings etc. But clearly with the right weaponry they can punch through it. And you can do the same by breaking through walls of your choice etc.
If you want to say that Battlefield destruction is like Crackdown, you're welcome to. I can't stop you from making that commentary. But to me, it's like saying baked GI and dynamic GI are the same. Except they aren't when things get moving.
Look at how debris does stay grounded.
Link 1
BFV for comparison.
https://www.youtube.com/watch?v=RIwOZs7csjc
I'm fairly confident, BFV has some very specific ways buildings explode.
https://www.youtube.com/watch?v=d0BFe5cGSjk
Not quite the same as the more physically based setup around crackdown.