I mean I try to do this weekly, and have done for a long time now. I've been close several times, including two bets which I was one or two bet builder bets off £500k+ so it can definitely be done. Honestly, these long shot bets are really the only ones I do these days. I usually put on a 4/5 fold accumulator for football, and then like a 5/6+ on the UFC. Sometimes combining the two to have a larger bet, but since most sites cap the amount you can win with UFC, that's usually for shorter odds.
I've even had bet builders breach the million mark, obviously never landed them. However, I've been close to the 500k like I said, and what I mean by that is I was like one goal off, and didn't get the corners correct (over market). So, painfully close.
So, while I can understand the scepticism, and definitely it could be a publicity stunt, I assume people bet like I do, and actually land them from time to time.
It never says it's impossible, the greatest example is literally said in OP, a guy who did it, so it is clearly not impossible to do so. However when you consider the odds, it is clear that it is very difficult to do. If it was such a simple thing, everyone would wager 1 dollar for each bet and would end up winning something in return as well and would all get rich and we would never have any money problems.
157k pounds is enough to get me to live comfortably forever without ever having to work for money and just enjoy life. So if it was so possible, I would have done it and would buy anything I want. So, it is not impossible, but not easy neither.