>Ramb advertises his "original game" as freedom
>When you play it, you can't do anything but kill if you want to progress at all; rather restrictive and railroaded for supposedly being "free"
>And notably, the freedom leitmotif is completely absent from all songs used in the game
The weird route is not actually freedom despite what Ramb and Spamton want you to believe.
Jevil believing he's the only free one despite obviously being locked in a cage is a metaphor for the route.
And remember, Genocide in Undertale ends with "SINCE WHEN WERE YOU THE ONE IN CONTROL?"

This dialogue is personally what cements it for me that Snowgrave was the original prophecy