I thought Polar believed in Erdrick.
The timeline of the Geno rumor and the Erdrick thing goes kinda like this, as far as I can surmise:
1) After the November direct, Polar's source's higher-ups reassure him that Geno might be DLC, as to inform him not to give up on Geno yet.
2) The Erdrick rumors have already been going on during all of this, mostly from Leakypandy and Hitagi, but then they spread elsewhere.
3) There has been no update on the Geno rumor, good or bad.
4) Polar's source knows nothing about Erdrick or his legitimacy, despite the large amount of rumors and leaks going around. He even called Erdrick 'Edward' because he had no idea who he was.
5) Polar is leaning into Erdrick and, as relayed by ForsakenM, is kinda 60/40 on him. This isn't because of her source, but the sources of other people and the corroboration from a 5ch leak that predicted P5R and a Granblue fighting game (whose predictability makes this rather debatable, it seems).
6) Insiders, as relayed by Fatmanonice, are apparently wondering if Erdrick was planned for base. Purely speculation on Fatman's side comes with his deduction that Erdrick and Geno might be on entirely different terms in the sense of negotiation, 'Square rep' business, and base game planning vs. DLC planning. They may or may not be in any competition to begin with, despite what the public presumes, but nothing is confirmed.
So, basically, Polar is making personal opinions from what she's been seeing, and her source hasn't heard about Erdrick at all. I don't know if her source personally weighed in on him beyond being literally like, "Who?" Considering he doesn't even know who Erdrick is, though, I'm willing to bet he's neutral and can't weigh in either way.