How do you know? Why not? It might well be exactly this belief makes things so complicated for everyone else.
Because I've experienced both modes of training/transmission. If you don't have the foundation of traditional daito ryu training, including katageiko, direct transmission and a whole host of other things, IMO, being shown solo exercises will not be enough to develop DR Aiki. It may well be excellent for transforming one's body, making one softer, more effective and healthful etc. I don't dispute any of that, but you will be missing too much "context" (that's the best word I can come up with) and ability to discern what to really concentrate on. This is just my honest opinion based on my experience. It may well make things complicated, but that's the way it is.