You're right to be skeptical but your alternative does not stand up to scrutiny. If a player indeed had a strong bite, milliseconds after the announcement would

You're right to be skeptical but your alternative does not stand up to scrutiny. If a player indeed had a strong bite, milliseconds after the announcement would be the worst time to execute. This is a time where almost all the liquidity goes away as market participants stand pat. If you had such a view, you would build your position over time, and certainly not incur the huge cost of making large trades at the lowest point in liquidity.