Probably best you ask whoever sent you these classes.

In general though %JSON.Adaptor has the %JSONFIELDNAME parameter, and not JSONNAME. Hence the error you got.

[There is an existing package shared in the past on the Community, see for example here, with some similar functionality, that did have this JSONNAME parameter. But I don't know if this is related in any way to the code you have]

[Note I also see you are using a %DynamicObject property ("Rationale"), and depending on what you expect to do with it, I don't know how well that will play with the %JSON.Adaptor export, per your use-case.]