Is pool: windows-latest (short format) officially supported for Microsoft-hosted agents?

### Question  
The YAML schema documentation only shows the explicit format:  
```yaml  
pool:  
  vmImage: 'windows-latest'  

However, many examples and real-world pipelines use the short format:

yaml
pool: windows-latest  

Is this officially supported?
If yes, can the docs be updated to reflect this?
If no, should it be avoided?