Unfortunately, not supported away from chromium derived browsers ATM: https://caniuse.com/document-policy (though given current market shares that sill means the majority of your user base is likely to have support)
I think we're a long way from standardisation just now. So the behavior of the header is verging on the undefined territory. It might do something. It might even order a grape soda. Hopefully it does what you want. It might not.