CSS isolation in Blazor

I don't know how exactly this new feature must be work in Blazor, but I think that the current implementation work wrong. Below some typical situation:

Layout for some blazor component:

<button>
  <span>Some Text</span>
  <Icon> ... </Icon>
</button>    

1. source scss file ...

2. that will be translated in to something like ...

3. after apply of CSS isolation we have :-( ...

4. Why NOT THIS????

And of course in DOM after rendering we have only button with scope id "b-l4md7xqlo6", but not span itself! Span don't have this attribute, and in my situation I don't need it. In other words, after applying of scope id, the result CSS not equal exactly to my declared CSS!

Any ideas?

Thanks, Nikolai