Learning from Unreal or even Godot to write a basic renderer is pretty wild. It would be like telling someone who wants to make a model rocket that they should study the Falcon Heavy.
Making a basic renderer in c++ is orders of magnitude simpler then trying to deconstruct a game engine that(according to google search) has over 2million lines of code.
The hard part if learning is figuring out what you do not know. The easy part is reading a tutorial or API documentation.
It's fine to just half-ass it if the interest is only superficial or for a hobby. Otherwise it might create a very unrealistic expectation in the student, because the gained knowledge by doing it like that is pretty worthless in a professional setting
But if one is to study rocketry without an aeronautics degree I'm guessing it's better to start from hobby level engines and vehicles and then scale up.
There is lot of added complexity due to size and mission constraints that is vehicle specific in Falcon Heavy, and I'm not sure how one would even use it as a learning platform - unless there is a university curriculum built around the vehicle.
There are lot of basics that model rocketry probably gives a good intuition for but then to my limited understanding it becomes (drumroll) rocket science.
And I did not study rocket science, but in my CS studies we definitely started with the simple ("hello world") basics, too, before touching real systems, so I would think, they do likewise. Because it makes sense. How can you understand and design something complex, if you cannot even make a simple version of it?
If you can't yet do so much as slap together some Estes kit and launch it in your backyard, what gives you the impression that you'd have the requisite knowledge to be able to gain anything from studying the Falcon Heavy?