Ruger1234 as i know otheros is supported on some debug models up to 3.20 its rumored 3.21 debug fw remove the otheros support but does not limit the downgrade function of the debug and im not sure if every debug the glitch can be pro formed on but there a lot more access on the ps3 debug then you think and no we can not install a functional debug fw on a retail you might get it installed but it will only install vsh which is no use without the flags being set for it... i hope that answered you question.
No OtherOS support in > 3.20 is kind of a no brainer
I was thinking in terms of countermeasures against the abilitiy to run arbitrary code. On a debug/dev unit there is of course no need for Linux or any OtherOS to run your own code. But there is still the issue of preventing hypervisor bypass.