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.