working with collections

collections.php

<?php

        $list = $this->Transacciones->find()
            ->distinct(...)
            ->select(...)
            ->contain(...)
            ->order(...)
            ->reject(...)
            ->sortBy(...);

        //debug($list);
        //LIST IS OK!

        $sublist = array_values($lista_orden_id->extract('entidad_id')->toArray());
        
        //debug($sublist); 
        //LIST IS **NOT** OK: I get values that were already rejected in $list 
        
        //question: How can I obtain a $sublist by manipulating $list without resetting the values to the original query?