SetFieldCssClassProvider not working or I'm not implementing it correctly

Describe the bug

Having trouble under 5.0 getting SetFieldCssClassProvider to set a CSS class for a valid/invalid form element ...

My implementation (or assumptions about when/where this works) might be incorrect. (Docs were generated from https://devblogs.microsoft.com/aspnet/asp-net-core-updates-in-net-5-release-candidate-1/#custom-validation-class-attributes-in-blazor and discussion with improved coverage on docs PR https://github.com/dotnet/AspNetCore.Docs/pull/21634. AFAICT from the PR, I did test, and it did work.)
The framework may have shifted between 3.x and 5.0.
There's a regression in how this works.

Coverage originally called for on PU issue https://github.com/dotnet/aspnetcore/issues/30459 with the docs PR at https://github.com/dotnet/AspNetCore.Docs/pull/21634.

Additional PU issues ...

https://github.com/dotnet/aspnetcore/issues?q=is%3Aissue+FieldCssClassProvider

To Reproduce

.validField {
    border-color: lawngreen;
}

.invalidField {
    background-color: tomato;
}

ExampleModel.cs:

using System.ComponentModel.DataAnnotations;

public class ExampleModel
{
    [Required]
    [StringLength(10, ErrorMessage = "Name is too long.")]
    public string Name { get; set; }
}

CustomFieldClassProvider.cs:

using System.Linq;
using Microsoft.AspNetCore.Components.Forms;

public class CustomFieldClassProvider : FieldCssClassProvider
{
    public override string GetFieldCssClass(EditContext editContext,
        in FieldIdentifier fieldIdentifier)
    {
        var isValid = !editContext.GetValidationMessages(fieldIdentifier).Any();

        return isValid ? "validField" : "invalidField";
    }
}

FormExample7.razor:

@page "/form-example-7"
@using Microsoft.Extensions.Logging
@inject ILogger<FormExample7> Logger

<EditForm Model="@exampleModel" OnValidSubmit="@HandleValidSubmit">
    <DataAnnotationsValidator />
    <ValidationSummary />

    <InputText id="name" @bind-Value="exampleModel.Name" />

    <button type="submit">Submit</button>
</EditForm>

@code {
    private EditContext editContext;
    private ExampleModel exampleModel = new();

    protected override void OnInitialized()
    {
        editContext = new(exampleModel);
        editContext.SetFieldCssClassProvider(new CustomFieldClassProvider());
    }

    private void HandleValidSubmit()
    {
        Logger.LogInformation("HandleValidSubmit called");

        // Process the valid form
    }
}

Exceptions (if any)

None

Further technical details

IDE: Visual Studio 2019 16.9.693.2781

OS Name: Windows OS Version: 10.0.19041 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\5.0.202\

Host (useful for support): Version: 5.0.5 Commit: 2f740adc14

.NET SDKs installed: 3.1.302 [C:\Program Files\dotnet\sdk] 5.0.202 [C:\Program Files\dotnet\sdk]

.NET runtimes installed: Microsoft.AspNetCore.All 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.WindowsDesktop.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

dotnet / aspnetcore