It's the norm here whenever we see a ceiling fan in an older house. Either there will be no box or it will be a 3/0 with 8/32 machine screws bent inwards to fit the bracket onto the box. Have also seen boxes held in by plaster only holding a ceiling fan, and once I saw a fan installed on a remodel box with nothing but the plastic ears holding it into the drywall ceiling.

Yeah, I've seen nightmares before but this one took me by surprise. I had done a pretty good inspection of this house when my daughter bought it several years ago. I know this builder used ITE Pushmatic panels (there were other houses in the neighborhood we looked at). However, this house was substantially reworked by someone who appears to have known what they were doing (new CH panel all done very neat and correct). Of course, that was six years earlier and the house was a rental in between so anything could have happened.

The condo my son is in is newer but I suspect that they came originally with a 4' tube fluorescent in the kitchen (where you make the connections inside the fixture) and some previous "harry homeowner" hacked this one it.

Nothing as bad as the house I had in NJ where I couldn't figure out how the lights in the bedroom could possibly work until I found a hidden splice where they swapped the conductors in the 14-3 that were running between the two accessible points.

It will be interesting to see how many "been there, seen that" responses there are. Joefixit already voted that this is a SNAFU. As for amateur me, I had one in a 1950 house for a couple of years. I don't remember where in the time line I discovered it, but 7' of brackish water in the house, after the wonderful Corps of Engineers' flood walls failed after Katrina, "fixed" it so I did not have to worry about it anymore.

I wondered how anyone would do it too, but ronnatalie's explanation of a previous luminaire with integral box makes a lot of sense.