You said it yourself, removing the option won't go well with basically any user today, and classifiers will remain fallible forever, so it won't be.

Yet, current non-users simply don't care about reading 4 system cards during roll-in and then keeping up with new ones every few weeks.

And, a solid adaptive thinking classifier is trivial compared to Anthropic's remaining tech stack. Task complexity estimation and model/effort selection are simple predictions with clear proxies in current data and millions of training samples generated daily by current users.