My 01. 5 has a stock double u-joint shaft without the rag joint. I put the single u-joint borgenson shaft with a new rag joint in the 91. 5. It has the same locking collar as the double u-joint shaft. If I had it to go over with, I would have used the double u-joint shaft in the 91. 5. I wouldn't worry about the shaft sliding apart, with or without the locking collar. I would be more concerned, but not very much, with the lower joint working loose from the steering box.
As far a a crash goes, it would take a massive frontal impact to cause enough damage to push back the steering wheel more than an inch or two, probably an offset collision with a bridge or a semi truck. At that point, you would have other things to worry about, like whatever was in the bed hitting you in the back of the head.