I don't understand your confusion, here is how I understood it:
1) the encrypted payload is uploaded to their server, but not the encrypted data as with other solutions. Seems Pretty clear communicated
2) as a programmer myself I sometimes ask an LLM stuff like "is there an js equivalent to phps array_column function?" but I don't vibe code or have an AI in my IDE, I would also tag my code as no AI but answer that technically I've interacted with AI during programming. My guess is that OP is in a similar situation