Ball joints in general are a tight fit and it's quite common for them to feel stiff when moving them by hand. Trying to move that tapered stud that is only about 2 inches long gives no leverage. I think that the manufacturers know they are a crude product so they make them tight and then they can wear themselves smooth. OTOH smooth is really nice so I have BJs similar to the Howes from QA1
https://www.qa1.net/suspension/ball-joints