--exclude seems to have no effect

When running `dotnet format` I see

`Warnings were encountered while loading the workspace. Set the verbosity option to the 'diagnostic' level to log warnings.`

`--verbosity diagnostic` tells me what the problem is:

`Cannot open project 'C:\source\repos\company\project\src\Infrastructure\Infrastructure.deployproj' because the file extension`

So I tried

```
dotnet format --exclude *.deployproj --verbosity diagnostic
The dotnet runtime version is '6.0.6'.
The dotnet CLI version is '6.0.301'.
Using MSBuild.exe located in 'C:\Program Files\dotnet\sdk\6.0.301\'.
Formatting code files in workspace 'C:\source\repos\company\project\Project.sln'.
Loading workspace.
Determining projects to restore...
All projects are up-to-date for restore.
Cannot open project 'C:\source\repos\company\project\src\Infrastructure\Infrastructure.deployproj' because the file extension '.deployproj' is not associated with a language.
[OMITTED: The remaining log looks totally fine]
```

Same behavior on folder level (`--exclude **\Infrastructure\*`).