I don't know about Kimi, but in my experience other providers like z.ai and minimax don't serve the same models via their subscription plans as they do with api pricing.

They're clearly quantised - spelling mistakes, wonky thinking section dividers, missing whitespace are the immediately obvious tells but along with that comes degraded quality, and it seems to vary based on time of day.

I wouldn't be surprised if Kimi did similar things with their subscription plans - try using it through openrouter and see if you notice different behaviour.