Angular Ivy strictTemplates true Type 'boolean | null' is not assignable to type 'boolean'

I've updated my app to 9 version. Everything is alright but I've problem with strictTemplates set to true. For instance this code

loaded$: Observable<boolean>
[loaded]="loaded$ | async"
@Input() loaded!: boolean;

I've got the error Type 'boolean | null' is not assignable to type 'boolean'.

This fix the error

@Input() loaded!: boolean | null;

But I cant see the point someone acn explain me, please?

The reason is because 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.

More about this here: https://angular.io/guide/template-typecheck#strict-null-checks

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"