My guess is that some health and safety weenie has decided that an unfiltrated rebreather smoke-hood will cause inspiration of harmful carbon monoxide that would exceed some promulgated OH&S recommended maximum intake per gasp. It's obviously preferable to "the system" (and would lead to less post-crash litigation) if the average pax would just oblige by ingesting much greater amounts of toxic smoke fire by-product, remaining in situ and just self-immolate after burning to death internally.

 Links to original articles are below (at bottom). It's not known if other smokehoods are similarly affected.

The EVACU-8 Replacement alternative Smoke-Mask