Finally, in daylight my aged eyes detect in the low-res image however provided the cat-5-looking stuff as well as the RG-looking stuff disappear into the wall at their lower visible extreme. Pre-existing and nothing to do with the fiber junction box. Which itself looks like a nicely-done "workman-like" job, from here.
Can't say I'd have finished off the stone veneer at the top quite like that, which, I guess, is why I quit doing that kind of stuff. Harder to sell a "do it right" job, and not enough satisfaction otherwise.