Ann: Quarterly Activities/Appendix 5B Cash Flow Report, page-54

I could be wrong, but I thought it was to attempt the reverse, but isn't guaranteed:

People will put a bulk of shares at below market value in the sell side. My understanding is whoever is at the top of the buy side will be number one on the list to buy at that lower sell order price... So then more people stack up higher priced buy orders to put themselves in a position to buy at that lower sell order price. But then at the last second, the sell order gets pulled, leaving all the buy orders to go through at higher values.

I find this is frequently done by bots though, which are capable of pulling sell and/or buy orders at the same time - so often both the higher buys and the lower sells get pulled, and only a few genuine sales go through on opening.

This is why most retail tend to avoid the opening unless they have conviction on a specific price they're willing to pay.