Not transpiling nullish coalesce with typescript

We are attempting to use ncc to transpile some typescript code into a single js file, and some of the dependencies include code that includes a nullish coalesce operator and it seems to simply ignore them and outputs it in the outputted js file which gives the following error when you attempt and run via node dist/index.js:

const d = options.lastModified ?? Date.now()
                                    ^

SyntaxError: Unexpected token '?'

I have the target defined both in the command: ncc build -a -e typescript --target es2015 src/main.ts

and in the tsconfig file:

{
  "compilerOptions": {
    "target": "es2015",
    "module": "commonjs",
    "moduleResolution": "node"
  }
}

Node version: 14

Start by reproducing the issue with ncc build -a -e typescript --target es2015 src/main.ts, using the shown tsconfig and Node 14. Inspect src/main.ts and the generated dist/index.js; done means the nullish coalesce operator is transpiled so the bundled file runs on the stated Node version.