I haven’t seen the programme schedule but stumbled across the Intuitive Baby Sleep Programme and the Possum Programme which is very much what you’re asking. From what I can gather, it’s about recognising when your individual baby is tired, not set nap times or awake windows. The theory is that a baby who is fed, clean, mentally stimulated when awake and genuinely tired, will fall asleep without fuss. It doesn’t worry about overtired.
With my first baby, he was VERY sensitive to being overtired. He would get in a mess, scream and struggle to then sleep. A nap schedule with strict awake windows worked very well for him and, while I was slave to the naps, it was much better than the screamy alternative. He would never have just fallen asleep when tired. That said, I do think I spent too much time worrying when I nap went awry, convinced I’d just ruined the entire day and night! So looking back, I’d have definitely had a plan but been more relaxed when it didn’t go smoothly because, well babies are unpredictable.
Second baby is now 9 weeks old, sleeps exclusively on me and can only be awake about an hour. Waiting to see what sort of baby he turns out to be around 3/4 months and whether he can go with the flow (as I’d appreciate more flexibility around the older child) or if he’s another one who needs structure.
Plenty of people take the “baby will sleep when it’s tired” approach, but I do think the success of that is partly dependant on the individual baby’s sleep needs and sensitivity to overtiredness.
Don’t tie yourself in knots over it. Just experiment a bit and see what works for you and your baby.