Why does Siri on my HomePod refer me to my iPhone all the time?

I've just bought two HomePods and hooked them up to my Apple TV, great all working as expected but I've been trying Siri to answer simple queries, for example, "Siri, what temperature should you roast a chicken" and Siri responds but rather than reading out something like "I've found something on the web, chicken should be cooked at 180C for 2 hours depending on the size of the chicken" it refers me to my iPhone which you then have to go and find and repeat the process. Should Siri not just respond reading out the basics and then ask you if you would like it to continue reading like it does on some subjects? Siri does exactly the same in my car using CarPlay (not cooking a chicken I might add, but for something I need to know whilst driving) and its not something you can do in the UK, refer to your phone whilst driving. Is this a Siri limitation or is there some setting to change?