Yes, that’s true, safety always comes 1st. Of course a baby should not be handled like an egg. Just imagine what they go through to be born and how they spend their 1st 9 months of life. They can be easily moved, curled up and posed, and believe me, they will feel pretty comfortable in all these bendy poses. Because they are used to that, being curled in the mommy’s tummy. But a photographer should be gentle and careful anyway.
The most important things to be protected are the neck and the head, because they have no neck control and it needs to be supported all the time. I definitely hold a baby’s head from behind all the time.
The best way to know how to handle a newborn baby during a photo session, is experience. But not only. You have to study a lot. You need to understand what is dangerous and what is not from the medical point of view as well.