The delta-v from Earth Surface to Moon is 15km/s.
So basically once you learned to go to space, going to the Moon is "only" 60% harder, even thought the moon is 1000x further away.
1. Walking on the moon implied a return trip which requires an extra ~3km/s.
2. Under the rocket equation the fuel requirements for more delta v grows superlinearly, which then awkwardly makes your rocket bigger, which requires more fuel...
3. 22 years prior a metal can went to space. The scale of a manned moon mission in comparison is absolutely nuts, even basic things like having rocket motors that can be relit is a large technical challenge.
Saturn had a massive payload, hence the gap in difficulty.
But my point anyway was that Saturn V is not 1000x larger than a soyouz, despite the moon being 1000x further away. Distance is not what counts in space.
Jokes aside, I hadn't heard the term before and from what I could guess/infer didn't see how it could be a measure between two places: https://en.wikipedia.org/wiki/Delta-v