More evidence supporting this: the new Disk Utility.app seemingly has absolutely no way to recover from a fusion drive being split up into an HDD and SSD (made a mistake partitioning it) -- you have to do it from the command line.
On the contrary, I booted the exact same machine into internet recovery (which gave me the Mavericks-era Disk Utility.app) and it literally had a huge warning that the fusion drive was partitioned incorrectly, and a repair button.
Why remove important features that still (have to) exist in the underlying utility? Like this is literally an operating system designed to run on only a handful of hardware, which is why people like it.