it also says don't attempt a routine before 3m
How are you defining what a routine is? To me, routine is doing anything according to the clock rather than according to the baby's needs. In which case, what would you do if you had older children?
I have to do the school run at 8.30am. Baby feeds usually around 6am and would still asleep at 8.30am. But I have to wake her and feed her at 8am so that she is not screaming on the way to school.
Likewise 2.30pm. Exactly as above. She has to be woken and fed regardless, because I have to take her with me to school.
There follows other routines. I need baby settled around 4.00-5.30 if possible, because I have other children who need dinner, their school reading done, spellings and times tables to be learnt, homework to be done.
Plus general sibling WWIII to be avoided in the after-school chaos.
I have to disrupt baby's sleep for things like getting the older ones to Brownies, Cubs, Beavers, Swimming, Rollerskating, friends houses, the park, the shops, open days at school, and so on and so on...
Bedtimes for three older children to fit in. They need baths, showers, a story and need Mummy for at least parts of that (although Daddy does most). Baby's bedtime must fit in around bedtime for the others so while she's still little (7 weeks), her bedtime has to be later when the others are tucked up and quiet.
Fact is, baby has to fit in with family.
I don't know if that would be described as routine? But structure and routine comes naturally when you have a large family. I definitely don't think it is a bad thing.