AFIK Scouts don't earn better goody huts than any other units. As a high level player (immortal/deity) the only correct starting build is 3 slingers for a quick upgrade to archers. I use my opening warrior and packs of slingers to scout, usually getting at least 5 goody huts (which nearly always nets me a builder) and a couple of city state envoys. I can understand a scout as first build, but why would anyone go for a builder first? There usually isn't even 3 useful tiles you can improve at that stage.
@civtrader6's detailed guide to a sub-T140 SV in another thread gives a good overview of a builder-settler (or scout-builder-settler) opening. If it goes well, you get something like:
- builder out for Craftsmanship eureka, start building settler;
- when settler is out (typically ~T21, sometimes earlier if you didn't build a scout), you should have Craftsmanship, switch to Agoge and build slingers (say, about 8 slingers in 10 turns).
- when army is out, you have early empire (capital at 4 pop, 2nd city at 2 pop), switch to colonization and build more settlers.
So say your capital is making 10 prod / turn when you build the first settler, then the choice of building the scout or not earlier (30 production) delays the first settler by 3 turns. I'll leave it to others to discuss about the value tradeoff. In any case, it doesn't matter if the builder is idle for a few turns or not, since you don't need craftsmanship right away, just after the settler.
Of course, this doesn't work exactly as planned if there are really bad barbarians, or a very early DoW from an AI. But like @civ6trader says, the defender's advantage in this game is enough (plus potential AI tactical mistakes) that you don't need that many units to repel a rush.
