Its not limiting. Its letting them buy coin at opening with accurate price instead of random price.
Have you ever heard of "Pump and Dump"? On newly listed coin? If you manage to hear it then that's the answer.
Its not pump and dump. Its finalizing orders order by order instead of with fixed price set by traders during fixing (like on stock market). You know how its done now?
1- Exchange opens setting orders
2- first user create sell order at x100 just for fun
3- second user create market buy order
4- third user create sell order at x1.2 for small profit
5 - fourth user created market buy order (0.01 sec after guy from point 3)
6- ......
n - n user created sell order at 0.8 of last price on other exchange
There are n-1 orders on market. And they hanging for moment that exchange will open trades.
Then exchange opens trading and is finalizing orders order by order. Means that guy from point 3 will buy with 100x price (because that the only wall that is on market that his buy order can hit in) and guy who made exactly same order type 0.01 sec after will buy at x1.2 price (because currently that's the lowest price available). That's ok for you? Or that's the stupidest way to open trades during listing and its done like that only to scam users.