Is IP recording Confidential?

I was interested in taking this implicit bias test [1] by Harvard, but hit the following line that's concerning me a little bit:

"IP addresses are routinely recorded, but are completely confidential."

What should I make of this? Why would they store my IP address, and can they guarantee they do it in a confidential way?

[1] https://implicit.harvard.edu/implicit/takeatest.html