Interesting 120V Sub Panel

Inspected a sub panel in an outbuilding today. The feeder had three conductors: 1-ungrounded, 1-grounded, and 1-equipment ground with a jumper from one ungrounded buss to the other relegating the panel to 120 volt only.

I have never seen this done before. Other than the fact that a 240 volt breaker will only have 120 volts is there anything hazardous about this particular arrangement?

In the photo (first attachment) , you can see the jumper from the left to the right side lugs. The feeder is attached to the left side lug from below.

BTW: I am aware on the other issues in the panel (e.g., non-isolated grounding buss, no bushings, etc.

Main panel was in a bedroom closet inside the house and had one severely heat damaged grounded conductor in it. Possibly due to loose screw and corrosion on the buss. Screw and copper conductor coloring has changed due to heat (second attachment).

It’s an amateur installation and I wouldn’t hesitate to call it that, but there’s no hazard in this practice.

Thanks, that’s what I figured, but wanted to double check.