I agree that TSMC doesn't have to worry about Intel stealing a large amount of their volume. But I do think that Intel poses a potential threat.
Intel has decades of proof points that they can be a technology leader. If they stay on track with 18A and 14A they may be the tech leader again. Intel seems to believe this currently.
Even with tech leadership I don't see Intel putting a large dent in TSMCs business (and they don't need to). What I do see as a possibility is Intel taking the tech lead and giving TSMC's customers a large bargaining chip that impacts TSMC's current de facto monopoly position. Losing the tech lead would limit TSMC's ability to freely set prices wherever they want them. Even if the customers don't move, TSMC couldn't ignore the fact they don't have tech leadership and would have to set price accordingly.
The problem for Intel is that nowadays "tech leadership" doesn't mean what you seem to think it does... ;-)
It doesn't mean having the sexiest most advanced technology on a Powerpoint slide, or even in a pre-production fab -- it means being able to mass-produce it in megafabs with good yield and at a competitive price, with good PDK and customer support, and preferably with a strong IP ecosystem.
For example, IBM have always been bullish about their fabulous advanced technology, including SOI, FinFET, GAA... -- but what they come up with in the labs has always been terrible to manufacture, as the companies who've tried to do this will know all too well.
Intel have historically aimed high with their technology and often hit (copper, FinFET) but also sometimes disastrously missed (10nm, EUV) -- and even when they hit, since their only real customer was the inhouse CPU group they didn't need to bother making the technology easy to use (terrible PDKs and support) because the design group just had to suck it up, and they didn't need to get really high yields or low wafer cost because their CPU product margins were so high -- I know for a fact that their yielded die cost has been up to 2x compared to TSMC in the past. And their IP ecosystem for customers to use is nowhere, unless you happen to be building CPUs like Intel... :-(
Changing this "raw technology is king, the customer will have to use it" mindset is Intel's biggest problem, just like it was for IBM. And if they don't -- which needs a total rethink in approach -- they have no chance of competing with TSMC, whose approach is "the customer is king, technology serves the customer"... ;-)