Not in my experience. All my Apple products have warranty starting from the day I activated them with my iCloud account.
I fully expect my new MBA coming to start from whichever date it arrives. It's been the case for everything till now. Also, Apple usually sends out invoices 1-2 days after the product delivers, if you buy online from the store. Or they send them out immediately if you buy from a physical Apple store.
It could be that what you are saying is right, about Apple "plus-minuses" on the actual delivery and warranty date, but I have never felt shortchanged on any of my warranties