I would say the translation across ontologies is carried out by “computationalism” in this case, rather than infra-Bayesianism itself. That is, (roughly speaking) we consider which computations are instantiated in various ontologies, and base our loss function off of that. From this viewpoint infra-Bayesianism comes in as an ingredient of a specific implementation of computationalism (namely, infra-Bayesian physicalism). In this perspective the need for infra-Bayesianism is motivated by the fact that an agent needs to have Knightean uncertainty over part of the computational universe (e.g. the part relating to its own source code). Let me know if this helps clarify things.
I would say the translation across ontologies is carried out by “computationalism” in this case, rather than infra-Bayesianism itself. That is, (roughly speaking) we consider which computations are instantiated in various ontologies, and base our loss function off of that. From this viewpoint infra-Bayesianism comes in as an ingredient of a specific implementation of computationalism (namely, infra-Bayesian physicalism). In this perspective the need for infra-Bayesianism is motivated by the fact that an agent needs to have Knightean uncertainty over part of the computational universe (e.g. the part relating to its own source code). Let me know if this helps clarify things.