TSMC being the only game in town is what's bad for the market.
Beyond some threshold, any meta-gaming of the market is bad for the market. It's like patents. When they were first instituted, they did some good by incentivizing innovation. Then, people started meta-gaming them, and used them as legal weapons to suppress competition well beyond the original intention.
I don't think there's a good argument that monopolizing a feature is good for the market, even if the means that allows it is technically legal.
What could be argued, is if legal remedies to this kind of meta-gaming might also be meta-gamed in return and become worse than the thing they were trying to remedy. This seems to always happen in a variety of forms.