You're assuming too much. It takes 5 Traditions to get a complete tree in and a single Ascension Perk. In the stream (unless I missed something) Wiz had four Traditions, in under two hours. Even if it was hot code, it makes sense that you can unlock a few Traditions pretty fast, since plenty of them give bonuses to building cost and colony cost and such. With that speed, you could get your first Ascension Perk in a few hours, depending on your playstyle. If you are either lucky enough to draw the necessary tech or if the first part of the Species Endgame perks don't require any techs, you could be joining the Shroud or rocking a God-Emperor in a few hours (assuming either of them are doable on the first stage). The Dev Diary noted that the second stage perk has a number or prerequisites, but there's no mention of the first having any prerequisites, other than the general note that all Ascension Perks have prerequisites. We'll see, I suppose.
Of course, while your guys are busy bending spoons in your little corner of the galaxy, another empire might be terraforming like nuts or preparing for a Ringworld or something. More than 20 ordinary Ascension Perks in the lot means that there are bound to be delicious bonuses or gameplay perks among them.
E: Re-read the Dev Diary in question. It noted that one of the possible Perk prerequisites is already having X Ascension Perks unlocked. My guess is that at least the second stage Species Endgame Perks have like a four Perk requirement or something, so you won't get them anywhere near as fast. They could also have the first stage locked until like the second or third Perk slot, if getting one early game is a problem.