The problem with security through obscurity (which is what this approach is analogous to), is that obscurity can't really be guaranteed, and you usually can't be sure exactly how your code will be implemented in the future. Here's some somewhat recent examples of that, where a Jeep was remotely controlled because the system's bus wasn't correctly segregated[1], and where an avionics messaging channel may be exploitable to send bogus information between planes and air traffic control[2].

1: https://www.wired.com/2015/07/hackers-remotely-kill-jeep-hig...

2: https://defcon.org/images/defcon-22/dc-22-presentations/Pols...