If Ukraine has taught us anything, no guarantees are enough.

Thankfully for Taiwan it takes more than 4 years to build and bring up a state of the art fab at a new tech node.

This is a pretty dumb take, honestly. Intel for basically forever operated using their own fab exclusively. After failures to maintain good yield rates at their 10nm node, they had the option of continuing to delay new product lines and be eaten by the competition in AMD, or give in to TSMC temporarily while they worked on fixing their fab in parallel. In fact, they were criticized greatly for not switching to TSMC much earlier.