Standard Rate is always "false"

Using the per diem api https://open.gsa.gov/api/perdiem/, if the Standard Rate is included in the response, it is not flagged as `"standardRate": true`

It appears to be the case for all these APIs:
https://api.gsa.gov/travel/perdiem/v2/rates/city/{city}/state/{ST}/year/{year}
https://api.gsa.gov/travel/perdiem/v2/rates/state/{ST}/year/{year}
https://api.gsa.gov/travel/perdiem/v2/rates/zip/{zip}/year/{year}

Additionally the response varies between year, prior to 2019 the response was:
```
"county": "STANDARD RATE",
"city": "Standard Rate",
"standardRate": "false"
```
Since 2019:
```
"county": "",
"city": "Standard Rate",
"standardRate": "false"
```
Should I use `"city" == "Standard Rate"` as the test for the standard rate? Have I misunderstood the point of the `"standardRate"` property? Is the property deliberately a String type rather than boolean?