The IP address 34.66.115.47 points to Google Cloud. I think there's a possibility the real address is legitimate and it's just a coincidence? Or maybe they're using a Tor-like service that "covers their tracks" by sending randomized data?
If you don't see any obvious reason for malice, I think you should email them and ask!
What kind of url is that? This cant be someone using a browser as normal on their own machine can it? Could they be trying to build a google form or document or something that embeds part of the sign up form?
Edit: unsubstantiated source [0] says that domain relates to Google app engine, so could be the person is working on a project that includes some form submission capability and somehow is using your site for testing
No I wasnt clear, I used the api at ipinfo.io to get the information about the ip address the parent had posted. That info pertains to the "problem" ip he is encountering, its not generated by some service at that address
If you don't see any obvious reason for malice, I think you should email them and ask!