That matches up with what they claim on their site:

CloudFlare does not actively block visitors who use the Tor network.

Due to the behavior of some individuals using the Tor network (spammers, distributors of malware, attackers, etc.), the IP addresses of Tor exit nodes generally earn a bad reputation. Our basic protection level issues captcha-based challenges to visitors whose IP address has a high threat score.

https://support.cloudflare.com/hc/en-us/articles/203306930-D...