There was a significant change in the way SP was calculated during Covid in 2020 using predominantly off course market and that system has been retained, so any data before that is now largely redundant. Similarly the Tote has altered their modus operandi in recent years which has seriously reduced their favourite-longshot bias, generally follow SP now and bigger divdiends only paid in bigger fields and at major meetings (particularly those involving World Pool).
Course market has altered significantly in recent years. There’s much less competition now and on course bookmakers generally following exchange (Betfair) prices.