We did the same and there is one big contradiction between this and the research linked: you're not holding them or walking until they sleep, you let the kids fall asleep on their own with the confidence that you'll be back.
In my country you get a monthly check in with experts for the first 6 months and then less frequently. Mostly to weigh and check growth and arrange shots etc. But they also take some time to discuss how things are going and publish a booklet per age group with advice to parents.
Their advice (based on other research) is to strongly avoid holding your child until she sleeps and instead recommend exactly what you did.
The reason is that if you are holding the baby, they fall asleep and then wake a bit or switch to lighter sleep some time later (like every human does periodically every night) they will encounter a different environment and the holding prent is gone. That's going to wake them up fully and get confused. So now you have a crying baby in the middle of the night that you need to hold again to get back to sleep.
While if they fall asleep in their bed, feeling safe that you'll be around, a few hours later if they wake up they'll determine that everything is still OK and as they expect it to be, and continue sleeping.
On a related note, if you sit with them while they're going to sleep, make sure it's "for a while before they go to sleep", not "until they go to sleep", or it becomes a contest where they stay awake as long as possible to keep you there.
Yeah, this is the advice I've always seen with sleep training. It's important to put them down drowsy but awake. I find this extremely challenging. If the lights are on I can tell, but when it's night time and I've got the lights out I have no idea when he's drowsy but not asleep yet, and he's extremely light sensitive so I can't just have a light on. So I often accidently put him down asleep and he actually does just fine.
I agree with not holding the infant until they sleep, that probably makes the greatest difference. I don't understand the check-ins, because they fall asleep so quickly anyway and we don't want to disturb them.
Kids and families are different, but do keep in mind that there is a world of difference between an infant and a 1-year old like the grandparent (perhaps literally?) poster was talking about.
There is nothing inconsistent about holding an infant and then sleep-training a 1 year old.
It's really age dependent. We didn't do it as structured as OP going back at exactly 3 minutes etc. When she was under 1 year old she would sleep within 5 minutes, so no need to go back.
Now that she's older and speaking, she sometimes doesn't want to go to bed and will tell you. Then it helps to communicate that you'll be back and they're not on their own. Gives enough comfort that I almost never do more than come back once after 10 minutes or so, and over half the time she's already sleeping. If not I just say good night again, hand back the stuffed animal that by that point has usually been thrown out of the bed and that's it.
In my country you get a monthly check in with experts for the first 6 months and then less frequently. Mostly to weigh and check growth and arrange shots etc. But they also take some time to discuss how things are going and publish a booklet per age group with advice to parents.
Their advice (based on other research) is to strongly avoid holding your child until she sleeps and instead recommend exactly what you did.
The reason is that if you are holding the baby, they fall asleep and then wake a bit or switch to lighter sleep some time later (like every human does periodically every night) they will encounter a different environment and the holding prent is gone. That's going to wake them up fully and get confused. So now you have a crying baby in the middle of the night that you need to hold again to get back to sleep.
While if they fall asleep in their bed, feeling safe that you'll be around, a few hours later if they wake up they'll determine that everything is still OK and as they expect it to be, and continue sleeping.