I don’t see how a splice could come undone in one drop and if it were coming undone how you would not notice it. I use the anchor a lot and the most I’ve ever had come undone was a single tuck. I have the Profish 1000 and I just went to 8 plait. It’s a more complicated splice and it is expensive but the line is a dream. The rope/chain transition is smooth coming through the windless and it lies very well in the locker.

Not sure what the purpose of the split link or swivel would be. Both would be weak links and I don’t know how they would get through the windless.

Another thing that will save anchors is to shackle the chain to the base of the anchor and then use heavy tuna cord to attach the chain to a shackle on the other end of the shank.