I think it doesn't matter. If the major question was if a 3rd party could have standing, and the answer was yes because they were a beneficiary, then all they need is to show that they were not given a benefit they were owed. If the reason they bought the tv was to use it on their wall, and would have benefitted from the source code to modify the tv or study how tvs worked etc, that would just be one possible benefit. Using the tv to excercise a right just to test if you actually have that right, or to use the tv and it's source as an example in the persuit of their operation which is to defend the gpl and the authors and users, that is still using the tv, and still a benefit that the gpl grants and that it's framers and users definitely intended to grant. The gpl goes on and on and restates the intent multiple times in multiple ways that the whole purpose is explicitly to grant every end user the right for any purpose and without having to justify it.

It would seem that this makes buying the tv just for the sake of the case perfectly fine by at least 2 different vectors, each of which would seem to be enough all by itself. 1 - You have to be able to test something to prove you have it. 2 - The overwhelmingly unambiguous writing in the gpl itself, let alone all the other surrounding decades of writings and speaking by both the people who wrote it, and the people who chose to apply it to their own works.

Maybe yet a 3rd factor, the SFC probably isn't trying to get paid money besides maybe the cost of the trial itself and some token, all they really want is for Vizio to do what they are already supposed to do. No matter why the SFC buys a tv, Vizio still has no excuse for not doing it's part, and all the SFC wants is for Vizio to have done what it should have, and it's not even something which costs Vizio anything. If they try to argue that SFC can't show they were actually harmed, neither can Vizio show that SFC is merely seeking to harm them.

My very biased (I want it to mean this) view anyway.