Here’s my take on it. YES abs strength is very important in keeping a porper lifting posture under load. However people think that this can be solved by doing trunk flexion movements (crunches, weighed crunches, cable crunches, leg raises, swiss ball crunches, etc.)… this is not the case…you need the “bracing” action to be effective, not the trunk flexion one. Why? Because when doing moves such as the squat, deadlift and the likes you must keep the lower back arched, you can’t do that if you flex the trunk!!!
So over-training the trunk flexion function might actually do more hard than good.
Ab rollouts, heavy overhead supports, plank progression, pallof press, woodchops are better movements for your needs. But the best might simply be to lift heavy without a belt (e.g. top half deadlifts beltless, top half squats beltless… as an assistance exercise, not a main one of course).