Sorry but a simple screenshot or a even a video is not a proof of work.
In this case it is (or in the context that you're describing) Even if you used Photoshop to create a screenshot, it literally is proof of *some* work (proof of work in Photoshop that is). In my case: I registered to the wallet, logged in, set up a pin and took a screenshot from the main page/dashboard.
Any developer could also create a dummy good looking wallet in 1 or 2 days...
Disagreed. This has actual functionality, therefore it's not an empty GUI.
if you have access to a wallet and say that this is not just a picture but a functioning wallet, then I think a good proof of his existence and work could be a video where you make a micropayment from it to any address that we could then see in a common network for example ethereum or bitcoin