A user requests a data stream, and receives it. That the user chooses not to execute or render a part of that stream is up to them - the data has already been delivered.

Interstitials, pop-ups and the like are simply contained within the stream, and aren't even guaranteed to run inside the browser. If the data connection is incomplete, modern browsers often discard data that is incomplete. Is that also illegal access?

The data stream is in the user's hands - and it is delivered before any Terms and Conditions are given.

It's similar to someone giving you a burger, saying it's free, waiting till you take the first bite, and then demanding that you eat the rest whilst they photograph you, and then use said photos to pay for making the burgers.

You could just walk away with your free burger.