I cannot see any reason why this should be true in Humankind (though it is certainly true in Civ because you are racing for one of several victory condition types). Remember, you are looking for most total stars, and stars will continue to require advancement in multiple different categories. In fact, specialization early actually has a benefit that it does not later: you can rush the next era by achieving quickly in a few categories. How does the game end? Is it when any player would advance out of the final age? Because then specialization is useful near the end to let you cause the game to end...but only if you were winning! Do we know how the game ends?