console.log outputs incorrect value when result extensions are used

[SevInf]

This code

import { PrismaClient } from '@prisma/client'

const prisma = new PrismaClient().$extends({
  result: {
    user: {
      fullName: {
        needs: { firstName: true, lastName: true },
        compute(user) {
          return `${user.firstName} ${user.lastName}`
        }
      }
    }
  }
})


async function main() {
  await prisma.user.deleteMany()
  await prisma.user.create({
    data: {
      firstName: 'Boaty',
      lastName: 'McBoatface'
    }
  })

  const data = await prisma.user.findFirst({
    select: {
      fullName: true
    }
  })

  console.log(data)

}

main()
  .then(async () => {
    await prisma.$disconnect()
  })
  .catch(async (e) => {
    console.error(e)
    await prisma.$disconnect()
    process.exit(1)
  })

Outputs {firstName: 'Boaty', lastName: 'McBoatface' } which is incorrect. Expected result is and object with only fullName property.
However, this:

 console.log((data as any).firstName)
  console.log((data as any).lastName)
  console.log(data?.fullName)

Outputs:

undefined
undefined
Boaty McBoatface

So, the returned value is correct, just console.log displays it incorrectly.