hours worked uncoupled from Percent complete

It seems that the work hours and Percent complete are tied together (for updating tasks).  is there a way to remove this feature?

I tried looking into the enterprise custom fields, but since it is a part of project OOTB, it is not there.   is there another place i can find and change this?

or perhaps a workaround?

for example,  i have 1 person assigned to a single 8 hr task,   due to some unforeseen circumstance, he has worked 6 hours and is only 50% done,  however, when he goes to his tasks to update his work, he can not enter both of these at the same time.

he can either update to 50% done (4 hrs filled in automatically )

or he can enter 6 hours worked (75% done filled in automatically, overriding his 50% done if entered)