Tailwind Config: Why does module.exports work in my case, but export default doesn't?

[phillipmohr]

• I was getting the error main.css:1:1: The text-largeclass does not exist. Iftext-largeis a custom class, make sure it is defined within a@layer directive.
• My package.json has this line "type": "module"
• text-large is defined in my tailwind.config.ts:

module.exports = <Partial<Config>>{
  theme: {
    extend: {
      fontSize: {
        large: '1.3rem'
      },
...

• I used it with the layer directive in my main.css

@tailwind base;
@tailwind components;
@tailwind utilities;

@layer base {
    h2 {
        @apply text-large font-semibold;
    }
}

I was only able to fix the issue by changing export default to module.exports and I wonder why? Am I not using ECMA module due to the "type": "module" option in my package.json?