According to Apple, if you opt-in to 'limit ad tracking,' "advertising networks using the Advertising Identifier may no longer gather information to serve you targeted ads. In the future all advertising networks will be required to use the Advertising Identifier. However, until advertising networks transition to using the Advertising Identifier you may still receive targeted ads from other networks."
In other words, opting out shuts down the Advertising Identifier, but you still might be tracked until UDID is permentately disabled. Apple is just waiting to let advertising networks adapt to the new setting. Sheesh, I love my privacy - just for privacy's sake. But there's nothing tricky about this.
What you say is absolutely correct, however, the point is that it in fact tricky
in the sense of going into settings, and turning ON the option to limit ad-based tracking. Tricky, not
in the sense of how ad based tracking itself works : you explained the technicalities of how it works, but that's beyond the point. It's tricky
in the sense that the end user has NO option to completely
opt-out. Opt out
in the truest sense of the word. In case you're wondering, personally, I give two flips about who tracks my device usage or app usage, I'm merely illustrating the point you missed about this discussion.
Casual users might be convinced that enabling this option will greatly limit the tracking that happens, but there's no defined scale as to how much lesser
would they be tracked. Perhaps, tricky isn't the correct word?