Tan’s purchase needs a public market, a quoted price he did not set, a blackout calendar that makes the timing legible, and an audience that reads Form 4s. You have none of the four. There is no window, no print, nobody to signal to, and no mechanism by which buying more of your own private company changes anyone’s estimate of it.

The honest analogue is uncomfortable rather than actionable: you are already at Tan’s 100% concentration without his liquidity, his ability to size the position, or his exit. The thing worth borrowing is not the trade but the question behind it — whether the blended cost of everything you own in one company is something you could state from memory right now.