Their claim is that training on their solution is "unlikely but possible".

Consider this scenario.

Has a google crawler read my new novel, which I may or may not have posted on my blog, page by page, as I wrote it?

Can you, without knowledge of what I have actually done, claim that the google crawler has not seen the novel?

Without any evidence that I have posted the novel online, it might be tempting to say that the crawler has not seen the novel, but what if I were in an adversarial position against Google on this topic and were challenging them to make that claim. You would wonder if I were hoping Google to overreach by making a definitive claim without taking into account some action that they had no knowledge of. It becomes difficult to use the scientific expression "There is no evidence for this" when there is an accusation of malfeasance because it can be so easily be conflated as "You can't prove we did it". It seems like the best you could say would be 'Unlikely, but possible'

I'm not taking them at their word, sorry. Genuinely, there is no reason to.