I think it is very risky to have such high expose to a high risk investment option like Bitcoin. Only 15% of my total investment portfolio is in Bitcoin and other Crypto currencies, so if something goes wrong, I still have 85% invested into other options and I would be able to take a hit and still survive.
Younger people can still risk a higher percentage exposure to risk, because they have time on their side to recover, but older people should never have a high percentage of their total portfolio invested into high risk investment options like this.
Everyone's situation is different and you should make decisions like that, based on your future needs.
Of course the bigger the capital the more relaxed and safer options are at your disposal. Some people have to gamble it or would never make it.
15% of a thousand dollars, or 15% of a million? You can't answer that, but the smaller your capital the harder choice it is.
But what if this guy can afford to have half his net worth frozen? he can literally sleep over bitcoin taking a dive, and wait the needed years for its recover, some people just can't (again those with smaller capital to begin with).
Or as the saying goes, never afford what you can't afford to lose. Maybe he can literally lose half his net worth and still be fine, so he is gambling it.
I'd say, he will make it. But i don't know at what price he bought, bitcoin relative to fiat price will probably rise (slowing down overtime, but up).
Now if he depends on this investment, then he could get in trouble, as you say. Hopefully he doesn't depend on it and can sleep comfortably.