Webhook Builder website rejects Google Forms parameters

I was experimenting with some ways of logging data and one thing I came across was using POSTs to a “Google Form” that adds a new line to a Google Docs spreadsheet. I did some digging and figured out a URL and form parameter that successfully adds new lines to the Google spreadsheet using cURL. However, when I try to set this up using the Webhook Builder site as a new integration, it fails with a red “Bummer!” box at the bottom. I dug through the console a bit and found an error about the form parameter containing the “.” character.

The form parameter that Google uses looks like “entry.758284671=Text To Submit Here”. Were the developers a little overzealous in their validation by blocking the use of “.”?