Even outside of that, I can override the bitrate in some instances. But yeah, I was mainly talking about the necessary replication, cache, and transcoding (and I actually forgot about the multiple codecs, which they also provide, in addition to multiple resolutions/bitrates)
Not so much a feature of YouTube as it is a feature of HLS/Dash... but yes, it means you've gotta transcode the source video into multiple different bitrates.