For many Ethereum addresses Etherscan shows this:
Then when you click on the "b" link you see something like this:
So, this can be just a coincidence, right? Somehow the same public address was generated in all five blockchains but that doesn't mean it's the same person or entity behind each one of them - is that correct?
Reading this answer I got the sense that if you use the same private key in all these blockchains then you'll necessarily end up with the same public address in all of them. Is that right?
Now, if that's all correct then why does something like Blockscan exist? I'm guessing that if something like Blockscan exists that's because it's not just a coincidence that the same 42-character string is a valid public address in different blockchains - does that make sense? Maybe in some cases it's a coincidences but usually it's not?
What's the best way to think about this? (I mean, without inspecting transactions to see if the times match, etc.)