UserAttributes don't work on MudTabPanel

Describe the bug I am trying to add tabindex to tab buttons, so it should be selected when I press Tab key. I use UserAttributes, but can't see tabindex attribute anywhere in DOM.

<MudTabs Elevation="2" Rounded="true" Color="Color.Primary">
    <MudTabPanel Text="Tab1" UserAttributes="@(new Dictionary<string, object>{{"tabindex", 0}})">
        Tab 1 content
    </MudTabPanel>
    <MudTabPanel Text="Tab2" UserAttributes="@(new Dictionary<string, object>{{"tabindex", 0}})">
        Tab 2 content
    </MudTabPanel>
</MudTabs>

This dont work too:

<MudTabs Elevation="2" Rounded="true" Color="Color.Primary">
    <MudTabPanel Text="Tab1" tabindex="0">
        Tab 1 content
    </MudTabPanel>
    <MudTabPanel Text="Tab2" tabindex="0">
        Tab 2 content
    </MudTabPanel>
</MudTabs>

Expected behavior I see tabindex="0" on mud-tab div. When I press Tab key first tab button becomes focused.

TryMudBlazor https://try.mudblazor.com/snippet/mumlascbUfJfQbKa