I love Carmack but I always thought his conclusion there was unsatisfying. I think the issue with really long functions is that they increase scope - in both the code and mental sense.
Now your MinorFunction3 code can access all the local variables used by MinorFunction1 and MinorFunction2, and there's no easy list of things that it might access which makes it harder to read.
Separate functions do have a nice list of things they might access - their arguments!
Of course this technically only applies to pure functions so maybe that's why it doesn't matter to Carmack - he's used to using global variables willy nilly.
Also sometimes the list of things a function might need to access gets unwieldy, which is when you can reach for classes. So no hard and fast rule but I think increased scope is the issue with it.
Now your MinorFunction3 code can access all the local variables used by MinorFunction1 and MinorFunction2, and there's no easy list of things that it might access which makes it harder to read.
Separate functions do have a nice list of things they might access - their arguments!
Of course this technically only applies to pure functions so maybe that's why it doesn't matter to Carmack - he's used to using global variables willy nilly.
Also sometimes the list of things a function might need to access gets unwieldy, which is when you can reach for classes. So no hard and fast rule but I think increased scope is the issue with it.