On Shadow's reads - I don't think all of his reads were dependent purely on Eager. I think he planned to get some reads based off of how people reacted to him and how he treated others but it's not going to go perfectly as planned.
He had Penguin and Gamma as his next suspects after Eager.
263 explains his Penguin read pretty well. He thought Penguin had Eagersnake as null because Penguin was a hedging on his buddy. Gamma read is explained in
297. Then in
305, he starts trying to wagon Penguin because apparently, he wanted to see how Eager would react to a wagon on him.
344 also explains why he scumreads Gamma and Penguin together. The rest just seemed to be varying degrees of town and null and he doesn't really go into reasons but does mention them in his ISO.
You seem to not buy Shadow's assertion that Eager and Penguin could be scum because Eager was pushing Penguin. But bussing is actually pretty common. Your reluctance to bus isn't something that applies to everyone, and I can see why Shadow thought Eager was bussing Penguin.
I think the bigger point is just how genuine and in-depth his thought process was here. You can tell that he truly believed Eagersnake was scum because he was hunting for Eager's hypothetical buddies and analyzing how they interact with him. That's just at a level I simply found impossible for Shadow-scum to have faked even when I was reading as a spectator.
Shadow may have loved WIFOM but I don't think he's a strong enough scum player to be able to pull off what he did. Did you meta Shadow by the way? His scumgame is actually not very strong. Even in the game you linked earlier, he was lynched mid-game and he wasn't a strong, vocal voice amongst the town.
I don't think the quote you posted is a lie so much as Shadow just misremembering what happened.