Blazor provides as part of Microsoft.AspNetCore.Components.WebAssembly a set of extensions (docs) that augment the features of HttpRequestMessage like SetBrowserRequestCredentials or SetBrowserRequestOption specifically for WebAssembly.

Those extensions do not have anything special to Blazor (even if the package depends on Blazor), and would benefit for being available in BCL, so that non-blazor frameworks (Such as Uno Platform) can benefit from those extensions without having to import those 4 types locally.