Slaver is a native animal of Syrikos V and has been bred by the Amarrians from the time they first settled the planet more than a millennium ago.
Seems to hint at a xeno species (even if it doesn't clearly say as such), that has been bred and engineered for eons, and so mixing up more and more with the terran biosphere... Of course it could still be a remnant of terran importation, but I chose to take the term 'native' to its literal meaning...
What is the 'literal' meaning of 'native', though? Are 'native americans' native to the Americas or to Africa? What about Europeans? The Darwin finches - are they 'native' to the Galapagos islands?
'Native', in biology and in general, doesn't mean at all that something has it's evolutionary or historical roots where it is 'native' to.
Just the same for the Achura: While they are the natives of the Saiso system (PF states that they are "originally from the Saisio system"), that doesn't mean that they aren't descended from the original terran settlers.
Slaver hounds work pretty much like a carnivore mammal here on earth. We know they have pups/cubs: That doesn't make sense at all if they are not mammalians or don't show parental care. It pretty much explicitly excludes the option of Slaver hounds to be born as fully functional, self-sufficient, though small, hounds. That'd also mean you couldn't really train them, as behavioural plasticity would be narrower due to the constraint of them having the programs for looking after their own survival ready.
I don't think that in an arboreal setting slavers will jump from tree to tree - they are simply too big for that. If you look at the big cats that live in arboreal environments - Tigers, Leopards, Jaguar - don't jump around much on trees. If they hunt from the trees above, they rather work by sneaky ambush (PF says Slaver hounds drop from trees btw.).
Also, it'd make sense not to throw all kinds of 'features' into the bundle because they seem fun. In the end all the features need to be worked into one functional whole to be convincing as well as to work under evolutionary pressure.