In December last year, Apple CEO Tim Cook traveled to Phoenix, stood with President Joe Biden in front of a high-profile factory Taiwan Semiconductor Manufacturing Co. was constructing and said the facility would produce chips for the iPhone maker. The comments seemed to commit Apple to aid Biden’s goal of lessening reliance on foreign chipmaking facilities—namely in Taiwan, which has been under threat of a takeover or blockade by China.

But Cook avoided speaking an uncomfortable truth: The Arizona factory—which has been a focal point of the Biden plan and will cost $40 billion to build—will do little to make the U.S. self-reliant in chips. That’s because many advanced chips made in Arizona for Apple or other customers such as Nvidia, AMD and Tesla will still require assembly in Taiwan in a process known as packaging, according to interviews with multiple TSMC engineers and former Apple employees.