that are symmetric swimmers. This is more the loping style, but with enough fall and paddle angle you get a bit of the same idea in a symmetric stroke. Brooke Bennet is the extreme example.
In that style I believe its also a lot of rotational energy they are catching, because they work at high strokerates.
With the asymmetric loping style one side is used to jack the body up and the other one to let it fall in the downward angled paddle.
Ledecky is doing the same
You see she isnt moving that arm much when she falls into that angled paddle, she mostly stabilises it and connects it to her whole body. Thats far less exhausting than actively moving that arm backwards and she still gets some propulsion during that fall.
When the fall has ended and she start to bounce back on buoyancy she starts pulling harder again, working with the bigger whole body buoyancy - mass forces that are available.
The big negative is that you have to jack the body up before you can use the fall.
How to do that without expending too much extra energy?
That russian guy makes it all look pretty efficient and natural, but its still hard to defend/explain this style from a pure mechanical efficiency perspective.