Using ProteinMPNN *without* oxygens?

[gian-marco-visani-dyno]

Hi, I noticed that if I run ProteinMPNN on backbones without the oxygens, the model does not break; however, the designs look very different with vs. without the addition of oxygens. My question is: should I expect the designs made without oxygens to be non-sensical? if this is true, then I wonder why the model doesn't throw an error instead.