I experienced something similar, only with dark cat fur on a soft, off-white plush carpet.
I vacuumed hard and well, so that no particles or fur could be seen. The Challenger system then pulled quite a lot of additional fur out and rolled it into balls. I had to vacuum all the rooms over again while the carpets were still wet.
No, I have seen this fur phenomenon before.
Also, I have been in contact with a company in the midwest that calls themselves "allerganx", meaning that they clean to solve allergy problems. They use the challenger, and they told me that they often see the challenger pull deeply imbedded pet hair out of carpets that the vacuum cleaner didn't touch.