That's changing now. Apple won't be the only one to get N2 at launch, and A16 (TSMC 1.6nm node) is HPC-focused and Apple definitely won't get it first (rumors say NVIDIA) and I wouldn't be surprised if they delay it until a mobile-focused version comes out.
That's why I think this deal makes sense for Apple even aside from the political considerations. HPC revenue at TSMC recently surpassed smartphones. TSMC has jacked up prices- including on Apple. Apple and TSMC are going from a symbiotic relationship where TSMC needed Apple to fund the new node and test it out first, and Apple needed TSMC for manufacturing, to one where Apple is dependent on TSMC but TSMC doesn't need Apple in the same way. TSMC is raising prices because of the AI data center boom, but Apple can't afford to get into a bidding war for wafers with AI chip companies that have chips that sell for thousands each.
Apple despises supplier relationships where Apple is not the one with the leverage and generally tries to dual-source so it can play suppliers against each other. If the second supplier isn't up to par, Apple will often work with them for years to try and make them viable (LG Display, BOE, Luxshare, etc.). It makes sense to try to do this with logic chips too. Intel will obviously give Apple a sweetheart deal, while Apple can use the existence of a credible second supplier to stop TSMC from raising prices on it again.