It changes the built in action of the lure for worse, the split ring is added for the bait to have a free swing action ( like if you tied a loop knot, for ex: Rapala or Duncan knot ), if you clip the snap to the split ring then instead of having 1 "joint" ( split ring/lure eye ) you have 2 "joints" ( snap/split ring/lure eye ), what happens is as the lure wobbles one joint goes one way while the other joint goes in the opposite direction so the bait wobbles correctly when both joints are aligned but incorrectly when the joints are moving in opposite direction ( it rolls on it 's side ), in a lipless crank is not easy to detect the split seconds when the bait rolls because the wobble is very tight and fast but it 's easy to detect on a lipped crank, when you reel in you feel the bait wobbling intermitently instead of continously.
Don 't take my word for it, do a test and you will notice the difference in the wobble.
Back then during the age of the dinosaurs when I began fishing I used to fish with snap/swivel combination on everything ( yeah, so I wouldn 't have to retie every time I changed lures : ) I didn 't know the effects the snap/swivel were doing to the action of my baits, then I read that most pros in those days did not recommend the use of snaps, they all recommended direct tie to the split ring. I changed my approach to what the pros recommended ( obviously, they were the pros, ya know ) and I did notice an increase in my catches with crankbaits.
Then I had the idea of removing the split ring and using the snap instead, it 's the same thing but instead of having my line attached to the split ring I have it attached to the snap and it 's a lot easier to open a snap than it is to open a split ring when you want to change a crank. But I used "El Cheapo" snaps until the day came I hooked a nice fish and lost it along with my lure, lesson learned ( never ever purchase cheap terminal tackle ! ). Nowdays I don 't even bother to remove the split ring in the cranks, I just snap to the eye.
Snaps can 't be "wrong", many hard swimbaits come with them to allow them to have a wider wobble, what 's wrong in the end is your application and the quality of what you use.