All these complications with SACD players
The complexities are largely hidden from the user and are there for backwards compatibility. Firstly, compatibility with CDs, then for those who only want 2-channel playback!
It is a bit like the multiple generations of USB and Ethernet, driven by the desire for more bandwidth.
Of course, the Direct Stream Digital (DSD) format employed by SACD is far simpler than the Pulse Code Modulation (PCM) used in CDs and Pure Audio Blu-Rays.
DSD is a stream of bits which just nudge the sound level up one or down one. All you need for playback is a low-pass filter in the mega-Hertz range.
Mathematically, PCM can be derived exactly from DSD, but not the other way round. The pioneering immersive sound label 2L.no archives its recordings in very high frequency DSD so they can be converted into multiple derived formats.
I acknowledge that DSD is difficult for editing and even more difficult for mixing which explains why very little pop / rock appears on SACDs compared with classical music.
2L.no uses floating point, not integer, master files for mixing.