It may depend on the individual hair (as so many things do!). I have 4b relaxed hair and 'cones dries out my hair, period. I try to limit my use of products have are loaded with 'cones and have had to do serious detective work to find the various names that are used for 'cones -- there are some that do not end in 'cones. I can get away with products that have small amounts in shampoos and washout conditioners, but when I use leave-ins with 'cones, they dry out my hair. Over time, I slowly began to realize this because the 'cones do make my hair feel like silk immediately AND split and/or dry ends appear to be "repaired". However, this is a quick fix and repeated use caused me more problems and the thing for me was that it took months for me to figure out that it was the 'cones -- it was very subtle because the products seem to work at first. I will try a shampoo or wash out conditioner that has 'cones, but I RUN from leave-ins that has 'cones listed high up the ingredients list.
There's a book call "Curly Girl" by Massey that explains how and why 'cones may cause problems over time.
Common 'Cones Snynonyms: Cyclopentasiloxane, Propyldimethicone, Hexamethyldisiloxane, Dimethicone, Cyclomethicone, Dimethiconol, Phenyl Trimethicone, Trimethoxysilicate (there may be more, but these are the ones I'm aware of . . . . )