I don't see that contradiction. Hip throws are not hard to learn in general. When it comes to sparring, they are easy to do in Judo sparring - because strikes are not allowed and the opponent is really close to you. They are hard to do in Karate sparring - because strikes and kicks are allowed and the opponent maintains distance. Japanese Karateka that I've seen have no issue with doing hip throws - possibly because Judo is in the school curriculum and everybody knows the basics anyway. European Karate instructors like to cross-train Judo to fill the gaps - and that's great. Will they be using it in competition? No. Should they still learn it for self-defense? Yes.