Nope, it is very possible to stream 4K @ less that 15Mbps-->> "Now COGO promises 4K Ultra HD streams on superslow 10Mbps broadband..They can reportedly deliver 4K content at less than 10Mbps, while Netflix currently recommends you have at least 25Mbps of spare bandwidth to stream 4K comfortably...." https://recombu.com/digital/article/4k-ultra-hd-10mbps-cogo-vs-v-nova