Just my experience in a company developing large complex system.
- We in a subsystem team very often question the seemingly unwise or even stupid code or algrithem from other department or teams.
- We even wonder if those stupidity is deliberately done in order to keep the secret from being leaked when employee jumped to competitors.
- Some of these crazy mess may be due to inexperienced developers.
- We also often joked that these messy work could also be the act of people trying to keep the knowledge and competence within so it would be difficult to move the work away, a way to keep their job from laying off.
The effect is that if a person taking a chunk of code or sub-component to the competitor, the knowledge may be misleading even to the point of counter productive, wasting the time of competitor to know the right thing than saving them.
Now let's apply these experiences to the case of "defection" if it really happened. The person is in the 30s and not outstanding in his work, at best he is in possession of these confusing mess. It probably would take the US and UK more time in deciphering these junk than doing their own research without it.
Reverse engineering isn't easy, and if often useless. Just like China's advancement is not really based on reverse engineering as the west is trying to advocate, reverse engineering isn't going to help the west either.