In South Asian cricket, we have seen many players' careers destroyed due to politics. And here every board has bad politics. I can't find any reason not to keep Sadab Khan in the squad. As the series will be held in Pakistan. And Pakshithan's pitch is helpful for spinners. Pakistan management should have given Sadab Khan a chance in this series. On the other hand, I am not surprised to not keep Fawad Alam on the team. We know that Fawad Alam is a good player in the Test format. But don't forget he is 37 years old. Perhaps now the Pakistan management does not want to keep any older players in the squad. But if Fawad Alam gets a chance in this series, he might have been able to perform well. England is a strong team, against such a team, experienced players are definitely needed.
Selection is a contentious issue for all the South Asian teams. India recently sacked it's selection committee after the poor performance of the team during the T20 World Cup. And I am sure that the situation is same for Pakistan, Bangladesh and Sri Lanka. And regarding Fawad Alam, I am not sure why the selectors are ignoring him. He got one chance to be in the test squad (July 2022) and could only manage 25 runs from two innings back then. And after that his performance in the domestic matches was also not good. That maybe one of the reasons.