That's somewhat disturbing....

Biotechnical robots. They're organics AND mechanics! Like a race of cyborgs.

But headcanon aside, addressing the actual question.. Feet can be pretty clunky at times. They are great when used right, but they are also these big heavy things that are on these awkward pivoting joints... great for stability, but if we imagine a race whose lives revolved largely around combat or high speed movement, agility and dexterity become more important, no? Having stubs instead of feet makes balance a bit more crucial, but once that's taken care of you get appendages that can go faster due to less weight and more aerodynamic design. Mechanical, biological, or otherwise, every single Isorian we know of is part of this military establishment. They even call each other "Knights" instead of Isorians. These people must be culturally dedicated to the art of combat, or at least have been for many generations. And in such a culture, fancy footwork would be important.

That's my pseudoscientifical explanation anyway. Obviously we're dealing with art logic in the end, but this is the best I can work out for more immersive exposition.

Also looking at an armor accessory of any kind shows we also have toes.

But still, /sigh

Ian mcConville thought the stubby feet of nendoroids were cute, and he used the stub feet as a concept for the knights. Also, nobody knows if knights 'evolved' or how they even came into existence. The creatures from Isora and Cradle could have been from a yet unknown process of coming to existence.

Please give me a picture of the biomechanichal almirians, because the last time I checked, they were burning zombies and a big about to become trojan burning king.