If the link to screen button is on a detail screen from a list, then it’s most likely the same button, but you are possibly viewing two different rows in the same sheet. When you added that button for the admin or the customer, was it already visible when you went to add it to the other tab? If it was, then it’s definitely the same button.
The independent screen configuration is there to allow you to break up each individual item in a list so the details layout for each list item can be designed independently. This is great if you have a static number of rows, but if the number of rows can change, then you are forced to designed each detail screen for each item in a list.