So you can save carbon and oil, the cost of a lawn mower, get great exercise, and impress your friends with your amazing skill. Why don't we all do it this way ? Be amazed.
Interesting. Definitely something for open spaces. I would make a mess if sything, I am confident.
My answer to lawn care on my quarter acre was to let much of the back yard go to understory meadow and to build as many raised beds in my front and side yards as I could fit. I have reduced the lawn by about 50% but am left with lots of strips of lawn between beds. A scythe would be hopeless, ...in my hands, at least, lol. Between my battery powered weed trimmer and my 25+ years old black and decker electric push mower, I get exercise and don't burn gasoline or oil directly. My mower is corded, so no battery to fade out after however many years. I have only run over the power cord once.
This is how we harvested hay. We kids walked behind the man with the scythe and gathered it up and tied it together with bunches of green grass and set it up in teepees to dry.
The scythe is the most frightening tool on the farm, right behind the bull castrator.
Sheep and goats make much more efficient lawn mowers.
My first job for the borough parks department when 14 or 15 included learning how to use & sharpen the English scythe which is held into the shoulder & pivoted around the front of the legs by moving with the lower arm only.
Here in Australia I eventually acquired a European style similar to that in your video. I've now had it for about 40 years, kept out of nostalgia.
There is a very good video of a competition between a petrol whippersnipper & a scythe. The scythe won by about 10 metrs over 20!