I don't buy it. Stress has nothing to do with getting kicked out of hack mode. Even the least stressful of interruptions, assuming it uses the local state registers that are used in hacking, can completely scramble your brain. The friendliest of comments from co-workers, assuming they're about hacking (but not your project) and require hacking thinking, can ruin it, if the comment turns into a conversation that lasts more than 60 seconds.

It's not about stress. It's about juggling a bunch of delicate state, and the state is being held in short-term memory registers that are easily clobbered.