az tag list and Get-AzTag show outdated tag values at subscription scope

### Description

When using the following commands at the subscription level:

```bash
az tag list
```

and

```powershell
Get-AzTag -Name "value"
```

I noticed that they return multiple tag values, including ones that are no longer in active use on any resource. This raises the question:

> Do these commands show all tags that have ever been added or modified in the past, regardless of current usage?

This behavior makes it difficult to determine which tags are currently in use. Could you clarify if this is expected behavior? If so, is there a way to retrieve only actively used tag keys and values?

Thanks!

### Script or Debug output

```PowerShell

```

### Environment data

```PowerShell
PSVersion 7.4.5
PSEdition Core
GitCommitId 7.4.5
OS Darwin 24.5.0 Darwin Kernel Version 24.5.0: Tue Apr 22 19:54:29 PDT 2025; root:xnu-11417.121.6~2/RELEASE_ARM64_T6030
Platform Unix
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1
WSManStackVersion 3.0
```

### Module versions

```PowerShell
Script 7.7.0 Az.Resources
```

### Error output

```PowerShell

```