moving task of subtype ListEmail from one contact to another using Salesforce apex

We are trying to move a task from one contact to another in a trigger. the task is created by ListEmail functionality.

We are getting an exception if re-assigning the WhoId. Exception:

Update failed. First exception on row 0 with id 00T1N00002TXv3jUAD; first error: FIELD_INTEGRITY_EXCEPTION, Related To ID: id value of incorrect type: 0XB1N000000XaCuWAK: [WhatId]

This is the sample code:

List<Task> task = [SELECT Id, RecordTypeId, WhoId, WhoCount, WhatCount, Subject, AccountId, TaskSubtype, AccountId__c, EmailListWhatID__c FROM Task where Id ='00T1N00002TXv3jUAD'];

system.debug('task = ' + task);
Task tk = task.get(0);
tk.WhoId = '0031N00001UvZDpQAN';
database.update(tk);