Tax relief on pension contributions to NEST worth more than your earned income

Hello, NEST recently advised me in an email that I can contribute more than my earned income as long as I don’t go over the annual allowance of £60,000. They also stated that they will claim tax relief on pension contributions worth more than 100% of my annual earnings. I gave them the following hypothetical scenario: Suppose my earned income is £30,000 and I would like to contribute an additional £20,000 of personal savings into my NEST pension pot, so a total of £50,000. The NEST advisor confirmed that I will need to contribute a net of £40,000 and that they would claim tax relief in the amount of £10,000. NEST stated the following in an email: “Tax relief applies to the contributions you make from your salary as well as any additional payments you make to top up your pot… That means the more you contribute, the more tax relief you benefit from.” Is this allowed? Can so contribute more than my earned income and are they allowed to claim tax relief on any pension contributions above my annual earnings?

Hi.
You can see guidance here: 
Tax on your private pension contributions
Thank you.