I think they say “Ask app not to track” because, if they say “Make app not track you” or something similar, they open themselves to huge lawsuits if (much more likely when) any app turns out to keep tracking users.

I don’t have the link handy, but Apple’s policies on this require apps not to track users across apps through other means if a user chooses “Ask App not to Track” at the prompt. The prompt text is just to show that Apple cannot technically prevent tracking even when a user tells the app they don’t want to be tracked across apps. There are a lot of shady practices being spread through common/popular SDKs used by apps.