My opinion on unnatural posing is that, even when taking safety precautions, they really are not good for the baby. The joints of newborns are very tender and, just because you can bend something a certain way while they are sleeping, does not mean it is safe. I know that a lot of photographers do it, and I'm not trying to be super harsh, but being in the medical field I have seen a lot of issues in infants from parents innocently doing much less contorted things than poses such as the "froggy pose".
From a photography standpoint, and this is likely just a style preference, but all of the unnatural posing seems very gimmicky to me. In 10 years I feel like people will look back and like "Why would you prop up a baby like that?"bI would think that a mother would much rather look back on images such as the ones you have presented and remember their sweet little baby in their natural, sweet, snuggly state. "I used to love when you were a week old and you would lay like a little frog when you slept" ... Said no mom, ever. Lol. I'm only joking, but that's just kind of my take on it.