As opposed to:
We're not there yet. I'm still dreaming.
The person in the anecdote above seemed to have a pretty "good luck"
Have you noticed, nowadays, games from such "big houses" tend to be not even worth pirating?
Just a major waste of time.
It is "guessed" using whatever mathematical model that matches the system.
Of course, if our whole theory is wrong, then the guess will be wrong and we won't know unless some condition arises where the predicted result and the observed result are different.
Ah right, I should have said that too: don't care about the dimensions. Just make a shape similar to that, which can be done using the vertices/dots in the provided paper (otherwise the print will be useless for the purpose of making the learning process easier).
You are just trying to learn how to draw nicely, right? You don't really need to care about properly matching some random example I casually picked off google images. You can change the dimensions at will as long as you understand what you are doing.
Whether you consider it whining, depends upon the tone you read it in.
I just read that comment and didn't feel annoyed enough to even give a downvote and the mod's reply seemed far too annoying.
The username on the other hand...
Essentially how that works.
At least in this case, you are using the same basics over and over again.
What to put where, is your imagination. The first 2 steps just explain how to put the stuff there. And since I recommended an eraser, I would expect you to know to use it when it comes to the point.
Since you desire to git gud at drawing, I would expect you to be good at imagining, which is the prerequisite.
So yeah. I this case, the rest of the owl is the same as the first circle and ellipse.
Oh and ignore the shadows. That comes in a completely different territory. You will need to learn shading, first. I'd never bother with that and just use a CAD software.
, or something like 
and then a 
The last one is not true isometric, but has a perspective. But you can make similar good looking stuff in isometric too.
To do perspective, you can't use the Printed isometric line/dot paper.
Instead, it has an additional step of choosing the infinity points and making your own lines for it.
I tried to find a good instructions page, but unfortunately, search engines just prefer YouTube videos (which I don't like to recommend).
Either way, this is one method that lets you git gud pretty fast, albeit in a different drawing form.
Another thing: The last example picture I showed, has circles and semi circles. Avoid those in your drawing at this stage. That requires you to learn an extra method.
That's where the science and technology comes in.
Also, isn't plumbing a technology? Or does it have to be in the Civ VI Technology tree to be recognised as one? I know Agriculture and Animal Husbandry is
Hey! As long as there is other people...
But if you were isekaied at the start of the apocalypse, which, let's be honest, is more likely than you surviving until post-apocalypse, you could become a monster magician!
On the other hand, if the apocalypse were Skynet...
Now just need it to start doing what you want it to do.