Right. I think the autogeneration of types should only be done if you have configured strapi to be a typescript project.
In fact, according to the documentation it should not automatically generate the type files, it autogeneration defaults to false (according to documentation). TypeScript configuration | Strapi Documentation.
I tried to set it to false manually via config/typescript.js and config/typescript.ts. It still generates the files. Seems like a bug to me.