Strictly hypothetically of course. But let's say someone made this wild claim whilst refusing to provide any evidence whatsoever. Would it likely be the truth in your opinion?
Particularly when you consider that anyone inclined to post such a thing must be craving the attention and approval of his/her forum peers.
It's trivial to prove that you control a Bitcoin address, so if you happen to control an address holding a large sum of Bitcoin, then it would be very simple to provide some evidence to back such a portfolio claim.
Fellow ozbargain member "cloudy" wrote a great post highlighting the logical gymnastics required to make these claims credible: