Insurance Co. says car must be in a locked garage

The bottom line may be cost but in the event a tree branch falls on it, hail damage, vandalism, theft etc., you will want your claim honored. With out the garage, well...
So far as tags go, in MD., 20 years and you can get Historic plates, DMV says you can only drive to events, parades or repairs. No daily, work, etc.
I have historic plates, Hagerty Ins. With an aggreed value, unlimited mileage, towing and membership.
My car is a beater, driver, work in progress. When I first applied to Hagerty, about 25 years ago, pictures of the car, garage were required. I set the value low and they agreed to cover it. Since then, the value has gone up and we agreed to raise the coverage.They said that they may ask for updated photos to verify that the car is being restored and not just driven. So far they have not, nor have they asked for an update of the odometer reading.
I like hagerty, the premium is reasonable and they are good people. I have missed my annual payment before and called them, as long as I didn't get in an accident during that time they renewed it, with no lapse in coverage.