Just because they're niche popular doesn't mean they're a good idea. That said the position of the people on those trikes doesn't look nearly as bad as the C5.

I have occasionally seen continental European tourists on those in Ireland. They struck me as a really bad idea for another reason. They're very low to the ground, which is probably good for aerodynamics but terrible for visibility for people in trucks, busses etc. There's no way I would cycle one on any normal road.

Some people do have a small flag sticking up but I don't think that's enough.

Recumbent bikes/trikes and C5s have a common (very serious in my view) safety flaw which is they have a very low visual profile at the eye level of most drivers, which makes them (I think) really hazardous in dense city traffic. The first thing your average West London driver taking their kids to/from school, ballet classes, drama club etc would see of a recumbent bike of any kind is when they had already gone under the wheels of their gigantic Chelsea tractor.

There's a subtle difference. The vehicles in your picture have moved the controls closer to the operator's hips; a little bit rearward, upward, and outward. This is probably a much more comfortable experience, especially for people whose arms are short relative to their torso length.

The wrist position is also rotated 90 degrees which looks a lot more comfortable with arms at sides IMHO.

Quite common to spot them in Germany or Netherlands.