Which Summer '19 (v46) sObject types are returning field describe results of soapType "tns:json"?

Apparently, there is a bug on Salesforce API v45.0 which leaks the new type JSON designed for Salesforce API v46.0. This is observed on the APIEvent object on the RecordData field whose type is json. Here is a plug from the documentation:

RecordData

Type json Properties Nillable Description A JSON string that represents the queried objects’ metadata. This metadata includes the number of results of a query per entity type and the entity IDs. Example

{ "totalSize" : 1,
  "done" : true,
  "records" : [ {
    "attributes" : {
      "type" : "Account"
    },
    "Id" : "001xx000003DMvCAAW",
    "Contacts" : {
      "totalSize" : 3,
      "done" : true,
      "records" : [ {
        "attributes" : {
          "type" : "Contact"
        },
        "Id" : "003xx000004U7xKAAS"
      }, {
        "attributes" : {
          "type" : "Contact"
        },
        "Id" : "003xx000004U7xLAAS"
      }, {
        "attributes" : {
          "type" : "Contact"
        },
        "Id" : "003xx000004U7xMAAS"
      } ]
    }
  } ]
}

This is already reported to Salesforce and they have worked on it. Currently, the support did suggest to disable the beta which wasn't what we expected though.

Known Issue: DescribeSObject call using the v45.0 Partner API are failing due to a complex type(json) that isn't defined in the WSDL