RePAYE / spousal income verification when filing jointly

Hoping some of the loan gurus here can provide clarification.

Looking into switching from IBR to RePAYE. Wife and I file taxes jointly. Part of the application asks if I can verify my wife’s income. I’m confused why this is relevant if we file jointly.

It appears if I can’t verify her income I’m classified as “single”, but wouldn’t my AGI be calculated the same either way? I can see how refusal to provide income of spouse would be relevant if filing separate to avoid gaming the system, but that’s not the case here. Won’t they see her income once I link our tax return?

What am I missing?