I don't think this is the case. It's just that it's more noticeable when it's the last bet.
Similar to how whenever you join a queue at a supermarket, it feels like it is always the slowest moving queue and people in the nearby queues are getting to the checkout much quicker... but actually what is happening is that you only notice it when you're in the slower queue... when you're in the faster queue, you never even think about it.
This might be the explanation for the "syndrome" they are talking about. The fact that the last bet is noticeable in an accumulated bet, makes it more crucial, and thus inflicts a sense of loss in our minds. We don't really happen to count all of the wins and losses in an accumulated bet, but instead, we most probably notice the first and the last bets when you put it in a spreadsheet.