TSMC could hand Intel everything they know and it wouldn't do them a bit of good before it's no longer relevant. Raw knowledge won't buy machines, train people to maintain them, build factories, tune the manufacturing processes, or make relationships with design partners. By the time Intel gets something running with something they pick up and starts thinking about making deals, TSMC will be off profiting from another breakthrough.

I've just heard that TSMC requires strict isolation for a period of years for any team that gets the detailed design specs that can lead to process knowledge, and that this now prevents several fabless companies from second sourcing without a second design team. I would think it would be even stricter with a non fabless client competitor like Intel.

I find it surprising that TSMC is going along with it, just because I would think it's hard to be sure some confidential information wouldn't leak. Unless this kind of institutional firewall works better than I think.

If I were to speculate, I would say that tsmc has a diversified enough customer base AND doesn’t see intel as a contract fab competitor. I would imagine if roles were reversed there would be a whole lot more concern.