Custom filter in server driven datagrid submits component instead of expected value

Question

I am creating a handful of custom filters for a server driven datagrid we are building. Up until now we've only used the default string filter which submits the expected format:

{ property: string; value: string; }

The screenshot below shows the console output for this as reference.

However when I replace the standard filter with a custom filter and I submit a simple string value through the ClrDatagridFilterInterface Observable next method, the datagrid state gives me the full custom component (see screenshot below).

I recreated this here: https://stackblitz.com/edit/angular-mr1yhy

Is this the expected behaviour of a custom filter? and if so is there a way to bypass this and just return the property/value combination?

PS. I know said interface allows both types (as shown below), I'd just like the first one and I can't seem to find the solution.

export interface ClrDatagridStateInterface<T = any> {
    page?: {
        from?: number;
        to?: number;
        size?: number;
    };
    sort?: {
        by: string | ClrDatagridComparatorInterface<T>;
        reverse: boolean;
    };
    filters?: ({
        property: string;
        value: string;
    } | ClrDatagridFilterInterface<T>)[];
}