This is my theory. They don't want other harnesses to use this because it costs them more. I don't know exactly how OpenCode works, but I'm assuming when people are using this plugin they are mostly using Opus for everything while Claude Code really only uses Opus for writing the actual code. It uses Haiku and Sonnet for almost all of the tasks outside of writing code.

So it hard for them to control and understand the costs of subscriptions if people are using them on different hardnesses that do things that they have no control over.