While I absolutely confirm that everything you said is true, it’s interesting that that call would be illegal in many European countries. And in many more you would at best get a „I can confirm this person worked on this position in this timeframe“

Hmm, interesting point, I did not know that. But, aside from that, while they cannot tell you that the candidate would not be ok, I did get hints on what to look out for.

I mean, you always have to take the previous employers' statements with a grain of salt, but if they say they really employed for just that project, it's also good info.