[soared]

Fingerprinting on your own sites is pointless since only third party cookies are being removed. First party cookies still work like normal.

[tpxl]

It gives you the ground truth with which you then correlate fingerprints from non-first-party domains.

[tedivm]

The whole point of it is to correlate it to other data using the same fingerprinting method. Google is often a first party and a third party, so they need a way to line all that data up.