Lambda Node18 type module, extension .mjs, results in ES error loading module

So, my package.json has type:module and the handler file extension is .mjs, so why am I getting this error?

ERROR (node:8) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.

followed by this one:

2023-06-27T13:49:12.742Z undefined ERROR Uncaught Exception { "errorType": "Runtime.UserCodeSyntaxError", "errorMessage": "SyntaxError: Unexpected token 'export'", "stack": [ "Runtime.UserCodeSyntaxError: SyntaxError: Unexpected token 'export'", " at _loadUserApp (file:///var/runtime/index.mjs:994:17)", " at async UserFunction.js.module.exports.load (file:///var/runtime/index.mjs:1032:21)", " at async start (file:///var/runtime/index.mjs:1195:23)", " at async file:///var/runtime/index.mjs:1201:1" ] }