"To be clear, wafer agreements are signed 2-3 years before the chip makes it into HVM and TSMC can build fabs faster than that so there will be no N3 shortages for anyone who signed a wafer agreement (apple, AMD, NVIDIA, QCOM, etc…). If they need more chips than what they signed up for, which happens, there may be shortages. This is how TSMC and the foundry business works. It’s all about the wafer agreements."

https://semiwiki.com/semiconductor-manufacturers/302408-tsmc...

Because that single customer paid in advance and book those capacity?

That is how it works in literally all other industry supply chain.