the fact that it would be discovered almost immediately.
If you give them a URL that does not appear in Google, ask them to visit that URL specifically, and then notice the content from that URL in the training data, it's proof that they're doing this, which would be quite damaging to them.
> […] it's proof that they're doing this, which would be quite damaging to them.
Is it? It's damning, but is it damaging at all?
I'm not getting the impression that anyone's data being available for training if some bot can get to it is just how things are now, rather than an unsettled point of contention. There's too much money invested in this thing for any other outcome, and with the present decline of the rule of law…
If you give them a URL that does not appear in Google, ask them to visit that URL specifically, and then notice the content from that URL in the training data, it's proof that they're doing this, which would be quite damaging to them.