Why horse racing markets move differently in the morning.
Most of a race's betting volume lands in the final minutes before the off. Turnover can double every few minutes in that window. That is also the window where any alert built on a multi-minute data refresh is already behind the market by the time it fires.
The morning window, roughly 9am to 1pm once bookmakers have priced up, works differently. Only a small share of a race's total turnover has traded by midday, and prices move over tens of minutes rather than seconds. That is a window where a short delay between a price cut happening and an alert landing does not erase the opportunity.
It is also thinner and more easily nudged than the pre-off market. A price can move on relatively little money, and that is a genuine risk. Requiring the same move to show up across several bookmakers at once is a reasonable filter against single-book noise, but it is not a defence against a coordinated early push. HorseWhale is built around the morning window for this reason, and logs the final pre-off minutes for the archive without selling them as an actionable alert.