That's what I thought, that it would be really greasy, but the people who do it say that isn't so. It seems that for a month it will be but then your scalp and oil production adjusts. I guess it makes sense that if we are constantly washing away the natural conditioning oils, and then replacing them with conditioner, our scalp makes more, and more. Maybe what it does is adjust when it's not being constantly washed away.
Also using henna/indigo and powdered herbs cleans the hair.
I also read that many use a very, very small amount of shampoo, like a tablespoon, mixed with all water in a shampoo bottle, and use it to wash the scalp. I've done that a time or two when I forgot to get shampoo, just a little bit left in the bottle, so I add water and shake it up to pour over my head. :D
A Black woman at work asked me how often I wash it. I said I usually wash it every other day, at the most I can go 3 days before it's oily. She said that she washes hers every 2 or 3 weeks and she likes the oils in her hair. She always wears it in a pony tail. Certainly a different type and texture of hair but I can see how it would be beneficial in conditioning.
I took this picture a couple of days ago. The ends don't look the best here, not usually that poofy. I got it cut not long ago at a salon, first time in 10 years. I trim a little myself whenever the ends get ragged.