That’s a good point that I hadn’t really considered; all those other “adult” sets are mostly static display pieces, whereas a hypothetical UCS-like Bionicle set would hopefully still have good (if not better than the original sets) poseability (even if it gets used as a display piece). And for that, I think you’re correct that it would need to have more Technic than most other adult-targeted Lego sets (still with System details, of course).