I run because I enjoy it, not because I’m trying to get somewhere fast. But I also bike because I enjoy it, not because I’m trying to get somewhere fast.
You seem to assume that because this thing is faster, it must automatically be less enjoyable. That’s not the case for bikes, why should it be the case here? In my opinion it sounds fun, and would probably be enjoyable.
How do you draw the line at "any kind of technology"? Isn't the bike itself "technology"? How about pneumatic tires? Or computer designed tread for optimal traction? Is a bike suspension too much technology? How about electric assist that can help you up a hill but won't propel the bike without you pedaling along with it?
That's a pretty weird idea.
Skis, snowboards, or snowshoes make traveling on snow, especially downhill, much more fun.
Bicycling, rollerblading, skateboarding (basically using anything with wheels) is very commonly considered more fun than running.
Most people who swim in cold water prefer using a wet suit rather than toughing it out.
And it's pretty fun to use a boat, surfboard, or scuba gear rather than be stuck swimming without any aids.
"All the work" is useless hyperbol. There are things that simply can't be done on a road bike. There are things that can be done on a road bike without a significant loss of safety.
Sport technology can reduce the skill required for certain things, but it also tends to extend the envelope of what is possible. It is almost never correct to think of technology doing all the work but rather to think of it as an ability multiplier.
There are of course, times when it is beneficial to practice without a specific piece of equipment. Either for a challenge or/and to hone a specific sub skill.
We’re talking about manually propelled bikes here. The bike isn’t doing all the work, but it is pretty essential in reaching the speed and sustaining the pace.
Sure you can argue that if you strap a rocket to your bike then you aren’t doing any work, but that’s not the case in either of these examples, so what’s the purpose of going down that tangent?
If I were to guess at their motivations, it might be 'what could make me go faster in the water and also be enjoyable'? I'd try it out of curiosity, sure, but I'm pretty sure it wouldn't last beyond the novelty for me.
The problem in this case is that the device is doing part of the swimming for you.