I guess the underlying question is whether access to a charger is in the order that the vehicle arrived at the Supercharger. The "TWO Tesla drivers" in your scenario presumably arrived at the Supercharger after the hypothetical Ford. (Teslas who were ahead of the Ford in the queue would not be delayed but ones arriving after the Ford could be inconvenienced.) The reference to a Ford is only an example; we do not own one or have any plans buy a Lightning but we do have an ID.4 that will presumably get Supercharger access in the next year or two. We do plan to get the retrofit and CCS adapter for our Model 3 (partly so that we have the option of using CCS chargers if and when that is a better option than a Supercharger).
Hopefully there won't be a lot of contention. Certainly there are Tesla drivers who will resent the appearance of any non-Teslas at the stations, and certainly of ones that will block a charger they aren't using. They might act, even if they got there after the Ford, to quickly move to the other stall, the one the Ford is about to take the right side charger of, and try to connect to it. They might try to express to the Ford driver how they are blocking 2 cars to use one spot.
But the reality is that a full supercharger with a line almost never has 2 adjacent spaces free at the same time. What will happen is single cars will pull out, and the Ford, though first in line, can't really use the spot. At best they could take it and not plug in, hoping the car to the left is going to leave soon.
Rather, what will have to happen is the Ford arrives when the station is not full and has no line, and has two adjacent stalls. They will then use the pair. After having done so, the station might be full, or fill up soon, and Teslas will arrive, and see the empty stall, and even try to back into it, to see that the Ford on the right is using the charger. They will then pull back out and wait. They could complain to the Ford driver, but she might not even be there to complain to.
Chances are nobody can use the stall, not even another Ford because a Tesla is in the next stall over. Unless all this is happening, as it should, at the end of the bank, making use of a parking space that happens to be to the right of the last stall. The empty last stall space will confuse but all chargers will be in use.
Ideally, as I said, Tesla and Ford apps will show the superchargers as having no available stall for your type of car, which will make you pick another charger.