"Company" field value is not updated on Change Task from the parent record
It is expected behavior.
By Default, "company" field is not mandatory on Change as well as on Change Task in OOB.
As it is not mandatory, neither it is asked to be filled by the user nor it is filled automatically through WF or script.
If the requirement persists, the customer might want to write a small script in Create Task activity in the workflow to auto-populate the company value based on the value filed in the change record company field.