Allowing time-tracking overlap when multiple users are assigned to the same subtask

I have a subtask setup with 2 subitem owners. I’d like each subitem owner to be able to track their work sessions during the same time frame. Currently, their times of work cannot overlap, however, I suggest that users have the ability to toggle time tracking overlapping on or off.
I.e., if there is an ability for multiple people to be included on a subitem, and work on the same item, then there should be an ability for their time tracking to be independent from each other, and able to overlap. If that can occur, then the ability to have multiple users assigned to the same subitem shouldn’t be allowed. Just my two cents for UX. There’s no reason there times shouldn’t be able to overlap since the time is logged per user, and noted in the time tracking column.