Isn't normal usage scraping in this case? Looking at whoogle-search/request.py it's "scraping" google urls via the python requests module. I'm reasonably sure google fingerprints requests and assigns different weights for "probably scraping". I wouldn't be surprised if this has a lower threshold for triggering their captchas and/or blocking.
I often trigger Google's captchas during normal usage. It seems to suspect the more "advanced" features like "intitle:" or "inurl:", or if I search too rapidly. I take being mistaken for a machine as a compliment!
That's understandable, a lot of exploit seekers use those features to find exploits e.g. "powered by [cms with known exploit]", Google (and Bing) are definitely are more prone to showing you a captcha for those searches, especially if you're looking beyond the first page.