Filling a hole in the ceiling.

At some point the loft was converted into a bedroom, en-suite and dressing room. Then they put a wetroom style floor in over the junction? splitter? box. So that’s been moved to under an accessible part of the landing, but he couldn’t feed the last cable through to it as there are no channels or holes in one of the joists. So this was the easiest/ quickest/ cheapest option.
Californian patch? Now you tell me ;)

The main problem with a California patch is that the paper around the hole creates an area proud of the rest of the surface. Trickier to fill and sand smooth than all the YouTube tutorials make out as you’ll have to feather it well for it to not stand out. In this instance, and in most tbh, I’d always cut a piece to fill the hole and attach it with a batten spanning the gap (like in this thread but with the batten inside rather than out), chamfer the edges on both the filling piece and existing hole and then fill over the top. If the gap filling piece is also slightly lower so that a thin layer of filler covers the entire hole area it makes life a lot easier when you sand and paint.

As for why sparkies need to drill into ceilings, it’s often a case of either pulling up a floor or putting a hole in a ceiling, and it’s hopefully a case of picking the least destructive and disruptive.