Yes, the principle or rule of fat over lean that is one of the fundamentals of traditional oil painting also applies when using water soluble oils, you're just using water (or a fast-drying medium) instead of turps.
The point of the fat over lean rule is to stop the upper layers of paint drying before the lower layers. If they do, there's a danger they'll crack when the lower layers contracts (shrinks) as it dries.
If you've been using the paint straight from the tube, you can apply another layer of paint directly over a layer of paint straight from the tube that's been sitting for two or three days without any concerns, because the 'new' paint is fatter than the paint that has been drying.
