Connecting smart switch (3 pole) at single pole terminal (end of line) switch

Question

An electrical novice, here, with some basic understanding.

I’m installing several smart switches around the house, where most locations require a 3-pole switch. I’ve had no trouble installing at these locations.

There’s one single-pole switch for an outside flood light I’d like to install a smart switch for, but I’m super confused.

As I understand, a standard single-pole switch in the “middle” of the house will have three wire bundles that intersect:

1. Upstream power bundle (hot, neutral, ground)
2. Downstream power bundle to carry electricity to the remainder of the house.
3. A bundle that branches off the upstream power to carry electricity to the light itself.

Right?

The switch I’m dealing with seems to be the “end of the line”, as it were, but there is only a single wire bundle (single hot/black, single neutral/white, single ground/naked). See picture

Questions:

1. How is this switch able to power the light? I’d expect there to be two wire bundles (upstream power bundle and a bundle going to the light), but there is definitely only one. What am I missing?
2. Ultimately, I want to connect this 3-pole smart switch that requires a neutral wire, but it doesn’t seem to be working. The switch itself powers on (blinking light), but the outside light will not turn on. How should I connect the wires if there’s only one wire bundle? See diagram from manufacturer for instructions.

Really appreciate your help!

Answer 1

I appreciate the help from others who told me about switch loops. I didn't know those existed.

To provide a formal answer, and some additional details that might help someone else, it was indeed a switch loop--with some variation.

I intended to turn the switch into a conventional format so I could install a smart switch that requires the neutral wire. When I climbed up to the floodlights to undo the switch loop, I was again surprised to find only one bundle of wires, where I expected to find two, per the standard setup for a switch loop (see image below).

Took me a bit to think through how this could possibly work. I realized that the switch loop (wiring switch?) from black to white must be happening at another light switch between the light switch in the basement and the floodlights. There was another set of light switches in the kitchen directly above the light switch in the basement and that's where I found the switch loop (wiring switch?).

Turns out, the kitchen was exactly the ideal place for the light switch for the floodlights, so I disconnected the switch in the basement entirely and installed a new light switch in the kitchen.

To avoid having to replace the two-gang electrical box with a three-gang, I replaced the single light switch with one that has two independent switches within a single unit (example image below).