Robert doesn't "know" who Starro is either. Normies and Robert know Starro from that one episode of Batman Beyond with the justice league, and that is it.
On the comics Starro might show up here and there, but he never had much else going for him, maybe in the legion of Superheroes, but who the fuck reads the fucking Legion?
So I don't buy for a fucking second Robert went "oh my goooooddd!!!" over a character he had to look up at the wikipedia later on, or the second he saw that tentacle, yep! That is starro, just like his 1960 debut against the JLA! that's my boy!!! yeah, uh-hu, totally happened.
I'm not one of those asshole that act as if people need to pass a ridiculous pop culture trivia before enjoying shit, let people like what they like, but I can't stand posers like Robert acting as if they have this investment over this D lister DC villain when in reality we all know that acting as if he is super duper excited for Starro is just another way for him to flex the "I CLAPPED WHEN I SAW THE THING I KNOW" which on Robert's mind, makes him the professional pop-culture commentator and the rest being the rest.
And this kind of attitude isn't exactly new, it is just taking a new shape on these internet age. But the core of the sentiment is "I know more than you", and if ever been in a comics convention in the 90's early 2000's, this was typical scene you would see everywhere:
https://youtube.com/watch?v=eTAGIkYsAdY
But really, acting out for fucking Starro? fuck off Robert.