Game Explain tested the problem and it seems the problem is if a significant part of you body covers the joy con the water that we are made of absorb the BluTooth signal from the joy con and cause the de-syncing problem, it can be fix if they boost the power the signal but the 20-hour battery life of the joy cons will suffer, or just leave it as is and put a warning about it in the news feed.
Game Explain Testing
Blunty Explains Game Explain
So basically already known problems that all BluTooth devices have.