Well...not exactly
You are not required to actually build the invention for which you are seeking a patent, so you do not need to prove that it actually works.
Yes, I am a patent holder - on an invention that actually does work. I had to prove that to my backers before they would sponsor the patent costs. I also had to do a lot of research to forestall any possible infringement actions by patent trolls.
There are lots of junk patents out there for inventions which have never been realized in practice - and never will be. You most definitely can patent an idea. Not quite so easy to enforce such a patent. The party with the most lawyers always wins those contests.
I pursued a patent a number of years ago. And an attorney friend told me that I had to demonstrate that my invention worked (either by diagrams or by a model).
So I built a model. And it worked perfectly. Unfortunately, it was too similar to another invention that had been patented about five years previously. Rats!
About 40 years ago the patent office issued two patents for magnetic motors and they had working models of both. They claimed at least that they worked well enough to issue patents, wonder what happened to them? One linear and one rotational. Made the front cover of Popular Mechanics.
You are correct. But, you have got to have least have a convincing blueprint. I tried to patent an idea for a clockwork ceiling fan gone used in areas without easy electrical access. The patent would have been easy. Getting someone one to make it was the hard part.