the async pipes return signature is something like <T>(input$: Observable<T>: T | null always, because it returns null to the template while it's awaiting a response from an asynchronous call.

you can do what you've done and allow null, or if you know it will never be null, use a non null assertion operator:

[loaded]="(loaded$ | async)!"

or disable type checking here:

[loaded]="$any(loaded$ | async)"

or for this particular case you could probably do something like this:

[loaded]="(loaded$ | async) || false"