I tbihnk the idea is to catch people who make the wrong bets. For example you mean to bet at $10 but you accidentally hit lay instead. or the opposite happens which is you mean to lay at $1.10 but you hit bet.

It also catches those trying to lay at under the minimum bet size as those people always put the $5 bet at $1.01 or $1000. If it does the wrong way around they get matched at the small/large odds.

Also some bots put in bids at the available price for bet/lay and dpon't check the market percentage. If the market has been delayed and there isn't much money in there and the bots have not checked this there is a chance they will back/lay at the extreme prices.

I hope that makes sense. Its basically trying to take advantage of people making mistakes.