If a wrd field is only read and written by JS, there's no point in having to use hson (and defining all the empty array fields explicitly with a type, or risking an error about variant arrays)
But the real point of JSON fields are that you can connect them to TS definitions:
<json tag="conditions" typedeclaration="mod::system/data/wrdschemas/config_types.ts#ManualCheckMessagesConditions" />
There won't be any runtime validation whether the stored data matches the type but the TS WRD APIs will pick up the type definitions