I’ve also found this Beast build post:
The photographs appear to show a fan splitter and the same four Molex connections. The owner also mentions that the SSD-cage power was initially left disconnected, which suggests that it has a separate connection somewhere in the supplied PDB harness. However, I still cannot clearly determine the complete power arrangement or how many independent PSU-to-PDB cables are required when all 15 HDD and 8 SSD bays are populated.
I’m waiting for clarification from 45HomeLab before ordering the custom PSU cables, as I want to understand the power arrangement fully and avoid ordering the wrong cables.
The post is encouraging regarding noise. The owner also lives in an apartment and reports that the Beast is very quiet with the large Noctua fans, although the top cover developed some resonance from the hard drives. That sounds manageable if it can be resolved with suitable rubber isolation.