Target license question: running mbox / at.js on every page even with no experiments adds to licensing cost?

An Adobe Target trainer told my client that mbox should be fired on pages where there are running experiments. This is apparently to reduce server calls, which would reduce licensing costs too. My client is using Target Standard.

Firstly, my client is already using at.js through Launch. They’re not using the old mbox.js at all. So is mbox even a thing for my client?

In Target’s interface, I see mbox referenced together with "Custom Code", e.g. when setting up a variation. So maybe it is still a thing even though they're using at.js?

But in all of the Target implementation guides for both client-side JavaScript and also for Launch implementations, the guides just say to implement at.js in all pages.

Then, in Adobe's pricing webpage at https://helpx.adobe.com/legal/product-descriptions/adobe-target.html, it states that Target Standard's license is based on Annual Page View Traffic. Based on the definition of "Page View", it does sound like running at.js on every page adds to the license cost.

So I’m not sure how to respond to my client about the trainer’s advice. I want to say that since they’re using at.js, they’re only paying for the server calls to Target from pages that have running experiments, and not from other pages where there are no experiments. But given what the pricing page says, I'm not sure if that is even correct. Yet, I feel that it's silly to limit at.js to certain pages because they could run experiments at any time on any page(s), which could mean constant toggling on/off of at.js.

Does anyone have any suggestions?