By the way I also needed to clear the 2nd select’s value when the 1st select changed, so I just added this under the “acf.add_filter” javascript:
$( '#acf-field_648b0890a2462' ).on( 'change', function( e ) {
$( '#acf-field_648b0852a2448' ).val( '' ).trigger( 'change' );
} );