Earlier quoted context omitted.
Wrong...they probably don't know your IP..but a agency that has global surveillance in place, can find your source IP quite easy.
All typical attacks on Tor are known for many years already. If you follow the advises from the Tor website, it will be very hard (nearly impossible) to find you. What do you mean by "quite easy"?
https://en.wikipedia.org/wiki/Global_surveillance#Infiltrati...
Edit: And that from netzpolitik (highly trusted german source) under 'A global passive adversary' that's the interesting part: https://netzpolitik.org/2017/secret-documents-reveal-german-...