Check the stackblitz: https://stackblitz.com/edit/angular-material-components-demo-5k6gey?file=src/app/app.component.html
When it has an initial value, it is not shown in the view, and when try to clear its value, its still showed buggly. The internal value is always correct, the problem is the view. The "clear value" button is also bugged, it internally clears the value correctly, but the value is shown bugged in the view.
I have already try 1000 things, including emitModelToViewChange: true, changeDetector, read every StackOverflow/GitHub post, etc. Using compareFn shows a view initial value of All (which is incorrect, because it should show "11" instead of "", and it doesn't fix the "clear value" bug.
I fixed both errors by adding this to the caller (app.component.html) of mat-searchable-select
[value]="searchGroup.get(filter.key)?.value"
and this to the mat-searchable-select.html
[value]="value"