Look at a building shell, even if you have zero clue about houses you can see if they used rotten wood. It looks like it will become a house. The more it progresses.. well, you can easily tell "that door shouldn't be where it is" and so on.
Now look at the code generated by $framework via "$tool new project $name". To a non-coder (or even just not using that language) it's not really discernible from a 90% finished product. Your house doesn't turn invisible because looked at it from the back.
Also house construction follows certain "easy" patterns a 5 year old can grasp - you need to start at the bottom, you can't put the paint on before the walls are in, etc.pp - give a coder of 10 years a project in another language without documentation and you won't hear anything in the direction of "it's more 10% or 80%" unless spending days. I'm not saying people building houses have an easier job - but it's palpable.