Edit: this is a bit unfair, if its a specific app they should be convinced to cache just to avoid unfair resource usage, but hotlinking in general should not be seen as a problem
It's a waste of donors money if someone is using this image as some kind of "is this thing on" test using hacked computers...
But this goes beyond that - it's some blind check of internet connectivity for the app, and doesn't get shown to the user. We're pretty sure of that, given that with the amount of noise that task generated, if there was an app featuring that image at least one of the ~ 90M daily "views" would've been someone reading these posts.
Now, given we want to be nice, we didn't just blindly block the traffic, although making requests without user-agent is against our UA policy https://meta.wikimedia.org/wiki/User-Agent_policy