That article says we aren't able to tie Geldhardt up to a long contract but i was under the impression he's signed a 3 year pro contract less than a year ago. The club said it was a long term deal and Transfermrkt also has him down as being under contract until the end of 2021 season. So i think that article might be mistaken about the significance of his age. Unless someone knows otherwise i thought Liverpool or any club want to sign Geldhardt have to buy him like any other senior player under contract.
There is also no way that the big clubs weren't onto his agent promising him mega money before he signed that last deal. If Geldhardt wanted to get to United, Liverpool etc quickly the best thing he could've done was not sign his contract and then left at the end of this season on a tribunal fee. So I think at least for now Geldhardt seems to think his future would be better served staying with us rather than taking his chance in a big clubs youth system.