I don't have any specific information about Hagerty or Grundy, however when dealing with insurance companies in general such requirements (often called 'exclusions' in the policy language), they are present to act as sort of built in contractual defenses. They of course have no idea what you are, or aren't, doing with your vehicle at any time, it only becomes an issue on the back end when you make a claim. At that time, they'll ask questions to determine if you've violated a policy provision (breached the contract) at which time they may issue a reservation of rights and/or fully disclaim coverage once they've completed their investigation. Their investigation can include recorded statements of you, inspection of the vehicle, witness statements... and if those reveal some level of fuckery you can figure out what may happen.
All that said, you may wheel it regularly without incident then get rear-ended while going to the corner store to get a pack of Twinkies in which case no red flags would likely be raised.
Matters of insurance claims and coverage are always fact-specific. One thing you can count on is that the (fill in the blank) Insurance Company will go to great lengths to not pay a claim if they suspect a valid reason exists to not pay.