Why do you say that? I regularly perform flat bench barbell skull crushers and parallel bar dips without elbow pain. Why would a cable attachment cause problems?
The long head of the triceps crosses the shoulder and attaches at the shoulder blade. Locking the shoulder/upper arm and only moving the elbow joint is arguably an “unnatural” way of isolating the muscle, and may cause/exacerbate elbow pain in some.
Of course, in practice it isn’t quite as black & white, but that’s why it might cause issues in some.