It is all about motives. While the general definition of 'altruism' attributes no selfish motives what so ever to the act being done, the scientific definition attributes the motive of one's own genetic preservation to the act.
Please explain why the general definition excludes helping members of one’s family and ingroup. So far you seem to be saying you exclude them because the scientific definition includes them, which doesn’t make sense.
I wouldn’t say the scientific definition attributes any motive, it just describes what is. Certainly ants don’t defend their colony to the death because they think, “I cannot breed, so I must do everything I can to protect the colony so my mother can survive to pass on more of the genes that I share.” They just do it. In the same way humans don’t sit around calculating what percentage of genes they share with the people they might save (we didn’t even know how altruism developed until recently, so for most of humanity’s history this wasn’t an option, and even now that we understand altruism we would think it ridiculous!), they just do it. Certainly we think we’re doing it for other reasons—love, compassion, patriotism—but we wouldn’t feel these emotions if they had not been useful in engineering humans to act altruistically.