Classic Car Insurance Hagerty vs Grundy

Some variatons in policy coverage for events most likely depend on the nature of the event.
Most sanctioning groups consider autocross as an individual timed competition, not racing.
Racing is when there is more than one vehicle competing to be the first at the finishing line.
Most road racing (and oval) involves qualifying sessions to determine the starting order. As those are not races to the finishing line that could have been what is meant by 'preparation for racing.'

There are are a number of other types of competition that don't quite fit neatly. There's non-timed track events with a variety of names, 'high speed autocross', hilllimbs, closed road rally under a variety of names, etc. Whether Hagerty and other insurers have different types of policies for different types of events I don't know. My guess is yes, at least broadly speaking. The risks vary with the type of event and sanctioning oversight, while the repair costs will relate to the vehicle values and repair costs.