Hard to say if they might be or owner intended to try to fit them to the car.
Here's two more from DMAC photo section with brackets.
Frank's Canadian 1926
1925 Star
Looks like they fasten above the body not through it. But both brackets are different from yours, all 3 are different at body mounting. Its almost like someone added them for same reason you say about top resting on the the tire. Friend of mine with 3 star touring's, doesn't think Stars had roof bracket's. Brochure's seem to agree
1926 A22 Durant here, just outside Ottawa Ont with none.
Where Are You From? Ottawa Ontario Canada
Do You own a car built by Durant? 1932 614 sedan made by Dominion Motors
My 1925 Star Touring has a hole in the wood at the top corners of the rear seats like the pictures show. You can feel it by running you finger along the upholstery. Unfortunately, the wood was so old it cracked when I lowered the top into the saddle.
Many years ago we had some of these recast using mine as patterns.
i sold sets to owners of cars other than Durants and Stars
they are probably "universal" to many different makes