And ... here's where your argument falls to pieces.
One, I didn't claim "developers of games (a type of software) should be able to predict all avenues of exploit and fix them before they happen". And if I had, it doesn't logically follow that "developers of other types of software should be able to do the same thing". Besides being a logical fallacy, and despite your assertion (which I will accept for the sake of argument though I think it's a gross oversimplification and an abuse of the term) that the development cycles are the same, that doesn't mean they are the same exact thing with identical functionality and context. One example: viruses run locally and a multiplayer game has a server and client. The rules are (or at least can be if you design them to be) different.
With authoritative server, you don't have to 'predict all avenues of exploit'. There is only one avenue -- the information given to you by the client. You can trust it implicitly (bad, even Rust doesn't do that) or almost not at all (not realistic due to resource constraints) or somewhere in between (more authoritative for some things, less for others). It doesn't matter what the client is doing on its side (or whatever avenue it is choosing, to use your wording) to tell the server that the player is flying, if the server is designed to heuristically analyze movement and disallow it, the client can't do anything about it.
You're still ultimately wrong because as long as there is communication between the server and the client then there is a way to mess with the server using the client. There is no way to make a hackproof server. None. Ever. It doesn't matter how isolated or controlled you think the conditions are, someone somewhere will manage to find a hole. Asking Garry to anticipate all these holes in advance, especially when this is Alpha, not Beta, not Release, is ridiculous.
You pretty much can't do what you're saying to do, and no matter the countermeasures there will be hacks. Maybe not tomorrow, maybe not next week, but there will be, and the hacks will happen in less time than it takes you to design the system.