Why is a class with this method not stable?

Question

PHP

public function addPatient(IBearing $patient){
    $this->patient = $patient;
  }

when parsing a class, the metrics mark it as unstable Instability = 1 , due to the fact that the class depends on other classes, by checking the interface.
Is it right to remove the check, or is it just to score on the metric?

Answer 1

Removing type checking would be wrong.

Answer 2

Rather, it is just a warning that the current class has dependencies, which is quite normal.