The 30 minute advice for newborns is relatively new, it was published in 2016.
As with all advice around things with pregnancy/ babies, it is at the extreme level. No research has actually been done on spending more than 30 minutes in a car seat and the research involved more preterm babies than full term, with low average birth weights. It doesn't define when they stop being a newborn either.
I'm not saying to chuck them in a car seat and drive for 5 hours, but the odd journey that is slightly over 30 minutes wouldn't worry me, especially getting home from hospital. Plus, I was in the backseat the whole way home anyway!
I also found that we didn't tend to go far for the first weeks and certainly won't be going far this time either. If I had a long journey to do, I'd stop every 45 minutes or so.
As with all things baby related, official guidance can be hard to navigate and make sense of We'll be having the same conversation about official guidance in relation to co-sleeping, perfect prep and weaning once the babies are here!