Selfishness can also mean whatever ones does for oneself in a rational context always includes what is non-harmful or beneficial for others as well. Doing things that don't harm others is good for us. Acting selfishly for our own benefit in a rational manner is best for all, one could say.

The caterpillar does indeed need to struggle out of the chrysalis, and other example. But that's not the general idea, although valid to suggest as applying. Anyhoot, I get your reservations, but I tend to agree with the overall message, as children from the same parents can sometimes mimic the selfishness and other times not be like those parents. The same can be said for the reverse with empathetic and supportive parents, but this is not to say to baby them like you seem to suggest. I can picture the general idea they are putting forth, despite there lacking a larger sample size or more verification. It's valid from my view of things. I don't think they, or I, tried to paint it as black and white, sorry if it came out that way by maybe not explicitly covering how these qualities aren't absolute, or exclusive.